WIP: preserve failed Codex job issue-242-hhdxc839

Refs #454

## Automated implementation (requires human review)
[SidebarComponent.tsx](frontend/src/components/layout/SidebarComponent.tsx) の1行を修正しました。`overflow-y-auto` を `md` 以上に限定し、スマホでサゼストがサイドバーの領域外で切られる原因を取り除きました。

差分を確認済みです。指定に従い、テスト・lint・ビルドは未実行です。実画面でのスマホ表示とPC表示の確認も未実施です。

## Automated review (not a guarantee of correctness)
```text
The change restricts sidebar scrolling to medium and larger viewports. No actionable regression was identified in the current diff.

```

## Verification
- Tests/builds/migrations were not authorized and were not invoked by the controller.
- Codex was instructed not to run them; its command transcript should be inspected.
- Do not merge before manual acceptance and required checks.

---------

Co-authored-by: Codex Night Worker <codex-night@localhost>
Reviewed-on: #456
Co-authored-by: テツノニジカ <969+codex-bot@noreply.localhost>

backend/db/migrate/20261115000000_add_post_count_index_to_tags.rb

@@ -0,0 +1,5 @@
+class AddPostCountIndexToTags < ActiveRecord::Migration[8.0]
+  def change
+    add_index :tags, :post_count
+  end
+end

backend/db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2026_10_15_010000) do
+ActiveRecord::Schema[8.0].define(version: 2026_11_15_000000) do
   create_table "active_storage_attachments", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.string "name", null: false
     t.string "record_type", null: false
@@ -630,6 +630,7 @@ ActiveRecord::Schema[8.0].define(version: 2026_10_15_010000) do
     t.integer "post_count", default: 0, null: false
     t.integer "version_no", null: false
     t.index ["deprecated_at"], name: "index_tags_on_deprecated_at"
+    t.index ["post_count"], name: "index_tags_on_post_count"
     t.check_constraint "(`deprecated_at` is null) or (`category` <> _utf8mb4'nico')", name: "chk_tags_deprecated_at_not_nico"
     t.check_constraint "`version_no` > 0", name: "chk_tags_version_no_positive"
   end

backend/spec/models/tag_spec.rb

@@ -2,6 +2,19 @@ require 'rails_helper'
 
 RSpec.describe Tag, type: :model do
   include WikiRecords
+
+  describe 'post_count index' do
+    it 'has a non-unique index on post_count alone' do
+      indexes = described_class.connection.indexes(described_class.table_name)
+
+      expect(indexes).to include(
+          have_attributes(
+              name: 'index_tags_on_post_count',
+              columns: ['post_count'],
+              unique: false))
+    end
+  end
+
   describe '#has_description?' do
     let(:tag) { create(:tag) }
 

frontend/src/components/TagSearch.test.tsx

@@ -0,0 +1,120 @@
+import { fireEvent, screen } from '@testing-library/react'
+import userEvent from '@testing-library/user-event'
+import { useLocation } from 'react-router-dom'
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+import TagSearch from '@/components/TagSearch'
+import * as api from '@/lib/api'
+import { buildTag } from '@/test/factories'
+import { renderWithProviders } from '@/test/render'
+
+
+const LocationOutput = () => {
+  const location = useLocation ()
+  return <output data-testid="location">{location.pathname}{location.search}</output>
+}
+
+
+const renderSearch = () => renderWithProviders (
+    <>
+      <TagSearch/>
+      <LocationOutput/>
+    </>, { route: '/ja/posts?page=3' })
+
+
+describe ('TagSearch', () => {
+  beforeEach (() => {
+    vi.spyOn (api, 'apiGet').mockResolvedValue ([])
+  })
+
+  it ('searches through native submission without an Enter key event', () => {
+    renderSearch ()
+    const input = screen.getByRole<HTMLInputElement> ('textbox')
+    fireEvent.change (input, { target: { value: '虹夏 not:TEST type:or' } })
+
+    expect (input.form).toBeInstanceOf (HTMLFormElement)
+    fireEvent.submit (input.form!)
+
+    const query = new URLSearchParams ({ tags: '虹夏 not:test', match: 'any' })
+    expect (screen.getByTestId ('location')).toHaveTextContent (
+	`/ja/posts?${ query }`)
+    expect (input).toHaveValue ('虹夏 not:test type:or')
+  })
+
+  it ('requests a search action from the software keyboard', () => {
+    renderSearch ()
+
+    expect (screen.getByRole ('textbox')).toHaveAttribute ('enterkeyhint', 'search')
+  })
+
+  it ('searches through the form when Enter is pressed', async () => {
+    const user = userEvent.setup ()
+    renderSearch ()
+
+    await user.type (screen.getByRole ('textbox'), '虹夏{Enter}')
+
+    const query = new URLSearchParams ({ tags: '虹夏', match: 'all' })
+    expect (screen.getByTestId ('location')).toHaveTextContent (
+	`/ja/posts?${ query }`)
+  })
+
+  it.each ([
+      { label: 'composition flag', composing: true, keyCode: 13 },
+      { label: 'legacy IME code', composing: false, keyCode: 229 }]) (
+      'cancels confirmation Enter with $label', ({ composing, keyCode }) => {
+    renderSearch ()
+    const input = screen.getByRole ('textbox')
+    fireEvent.change (input, { target: { value: '虹夏' } })
+    const uncancelled = fireEvent.keyDown (input, {
+	key: 'Enter', isComposing: composing, keyCode })
+
+    expect (uncancelled).toBe (false)
+    expect (screen.getByTestId ('location')).toHaveTextContent ('/ja/posts?page=3')
+    expect (input).toHaveValue ('虹夏')
+  })
+
+  it ('cancels Enter throughout composition even without keyboard IME flags', () => {
+    renderSearch ()
+    const input = screen.getByRole ('textbox')
+    fireEvent.compositionStart (input)
+    fireEvent.change (input, { target: { value: '虹夏' } })
+    const uncancelled = fireEvent.keyDown (input, {
+	key: 'Enter', isComposing: false, keyCode: 13 })
+
+    expect (uncancelled).toBe (false)
+    expect (screen.getByTestId ('location')).toHaveTextContent ('/ja/posts?page=3')
+    expect (input).toHaveValue ('虹夏')
+  })
+
+  it ('blocks direct submission during composition and allows it after confirmation', () => {
+    renderSearch ()
+    const input = screen.getByRole<HTMLInputElement> ('textbox')
+    fireEvent.compositionStart (input)
+    fireEvent.change (input, { target: { value: '虹夏' } })
+    fireEvent.submit (input.form!)
+
+    expect (screen.getByTestId ('location')).toHaveTextContent ('/ja/posts?page=3')
+    expect (input).toHaveValue ('虹夏')
+
+    fireEvent.compositionEnd (input)
+    fireEvent.submit (input.form!)
+
+    const query = new URLSearchParams ({ tags: '虹夏', match: 'all' })
+    expect (screen.getByTestId ('location')).toHaveTextContent (
+	`/ja/posts?${ query }`)
+  })
+
+  it ('selects the active suggestion without submitting the form', async () => {
+    vi.mocked (api.apiGet).mockResolvedValue ([buildTag ({ name: '虹夏' })])
+    const user = userEvent.setup ()
+    renderSearch ()
+
+    await user.type (screen.getByRole ('textbox'), '虹')
+    await screen.findByText ('虹夏')
+    await user.keyboard ('{ArrowDown}{Enter}')
+
+    expect (screen.getByRole ('textbox')).toHaveValue ('虹夏 ')
+    expect (screen.getByTestId ('location')).toHaveTextContent ('/ja/posts?page=3')
+    expect (screen.queryByText ('虹夏')).not.toBeInTheDocument ()
+  })
+})

frontend/src/components/TagSearch.tsx

@@ -1,6 +1,6 @@
 // TODO: タグ入力系すべてに同様の処理あるため共通化する．
 
-import { useEffect, useState } from 'react'
+import { useEffect, useRef, useState } from 'react'
 import { useLocation } from 'react-router-dom'
 
 import { useLocale, useLocaleNavigate } from '@/lib/useLocale'
@@ -10,7 +10,7 @@ import { inputClass } from '@/lib/utils'
 
 import TagSearchBox from './TagSearchBox'
 
-import type { ChangeEvent, FC, KeyboardEvent } from 'react'
+import type { ChangeEvent, FC, FormEvent, KeyboardEvent } from 'react'
 
 import type { Tag } from '@/types'
 
@@ -20,6 +20,7 @@ const TagSearch: FC = () => {
   const locale = useLocale ()
   const location = useLocation ()
   const navigate = useLocaleNavigate ()
+  const compositionFlgRef = useRef (false)
 
   const [activeIndex, setActiveIndex] = useState (-1)
   const [search, setSearch] = useState ('')
@@ -74,7 +75,34 @@ const TagSearch: FC = () => {
     setSuggestionsVsbl (false)
   }, [locale])
 
+  const handleSubmit = (ev: FormEvent<HTMLFormElement>) => {
+    ev.preventDefault ()
+    if (compositionFlgRef.current)
+      return
+
+    const parts = search.split (' ')
+    const match =
+	parts.map (t => t.toLowerCase ()).includes ('type:or') ? 'any' : 'all'
+    navigate (`/posts?${
+	(new URLSearchParams ({
+	    tags: parts.map (t => t.toLowerCase ())
+		       .filter (t => t !== 'type:or')
+		       .join (' '),
+	    match })).toString () }`)
+    setSuggestionsVsbl (false)
+    setRequest ({ query: '' })
+  }
+
   const handleKeyDown = (ev: KeyboardEvent<HTMLInputElement>) => {
+    if (compositionFlgRef.current
+	|| ev.nativeEvent.isComposing
+	|| ev.nativeEvent.keyCode === 229)
+    {
+      if (ev.key === 'Enter')
+	ev.preventDefault ()
+      return
+    }
+
     switch (ev.key)
     {
     case 'ArrowDown':
@@ -90,13 +118,12 @@ const TagSearch: FC = () => {
       break
 
     case 'Enter':
-      if (activeIndex < 0)
-	break
-      ev.preventDefault ()
       {
-	const selected = suggestions[activeIndex]
-	if (selected)
-	  handleTagSelect (selected)
+	const selected = suggestionsVsbl ? suggestions[activeIndex] : null
+	if (selected == null)
+	  break
+	ev.preventDefault ()
+	handleTagSelect (selected)
       }
       break
 
@@ -105,20 +132,6 @@ const TagSearch: FC = () => {
       setSuggestionsVsbl (false)
       break
     }
-    if (ev.key === 'Enter' && (!(suggestionsVsbl) || activeIndex < 0))
-      {
-	const parts = search.split (' ')
-	const match = parts.map (t => t.toLowerCase ()).includes ('type:or') ? 'any' : 'all'
-	navigate (`/posts?${
-	    (new URLSearchParams ({
-		tags: parts.map (t => t.toLowerCase ())
-			   .filter (t => t !== 'type:or')
-			   .join (' '),
-		match }))
-	    .toString () }`)
-	setSuggestionsVsbl (false)
-	setRequest ({ query: '' })
-      }
   }
 
   const handleTagSelect = (tag: Tag) => {
@@ -144,8 +157,9 @@ const TagSearch: FC = () => {
   }, [location.search])
 
   return (
-      <div className="relative w-full">
+      <form onSubmit={handleSubmit} className="relative w-full">
 	<input type="text"
+	       enterKeyHint="search"
 	       data-shortcut-focus-search="true"
 	       placeholder={message ('labels.tagSearch').text}
 	       value={search}
@@ -153,12 +167,18 @@ const TagSearch: FC = () => {
 	       onFocus={() => setSuggestionsVsbl (true)}
 	       onBlur={() => setSuggestionsVsbl (false)}
 	       onKeyDown={handleKeyDown}
+	       onCompositionStart={() => {
+		 compositionFlgRef.current = true
+	       }}
+	       onCompositionEnd={() => {
+		 compositionFlgRef.current = false
+	       }}
 	       className={inputClass (false,
 				      'px-3 py-2 dark:border-gray-600 dark:bg-gray-800 dark:text-white')}/>
 	<TagSearchBox suggestions={suggestionsVsbl && suggestions.length ? suggestions : [] as Tag[]}
 		      activeIndex={activeIndex}
 		      onSelect={handleTagSelect}/>
-      </div>)
+      </form>)
 }
 
 export default TagSearch

frontend/src/components/layout/SidebarComponent.test.tsx

@@ -70,6 +70,16 @@ describe ('SidebarComponent', () => {
     vi.spyOn (HTMLElement.prototype, 'hasPointerCapture').mockReturnValue (true)
   })
 
+  it ('limits sidebar scrolling to desktop to avoid clipping mobile suggestions', () => {
+    renderSidebar ()
+
+    // jsdom has no layout; guard the responsive classes responsible for clipping.
+    const sidebar = screen.getByText ('Sidebar body')
+
+    expect (sidebar).not.toHaveClass ('overflow-y-auto')
+    expect (sidebar).toHaveClass ('md:overflow-y-auto')
+  })
+
   it ('uses maxWidth without applying the container main-width reserve twice', async () => {
     localStorage.setItem ('sidebar:test-sidebar:left:width', '700')
     const onWidthChange = vi.fn ()

frontend/src/components/layout/SidebarComponent.tsx

@@ -339,7 +339,7 @@ const SidebarComponent: FC<Props> = ({
 	  </style>
 	</Helmet>
 
-	<div className="h-full overflow-y-auto p-4 sidebar">
+	<div className="h-full md:overflow-y-auto p-4 sidebar">
 	  {children}
 	</div>
 

frontend/src/pages/tags/TagDetailPage.test.tsx

@@ -35,6 +35,10 @@ const renderPage = () =>
 describe ('TagDetailPage', () => {
   beforeEach (() => {
     vi.clearAllMocks ()
+    tagsApi.fetchTag.mockReset ()
+    api.apiPut.mockReset ()
+    api.isApiError.mockReset ()
+    toastApi.toast.mockReset ()
     api.isApiError.mockReturnValue (false)
   })
 
@@ -51,8 +55,11 @@ describe ('TagDetailPage', () => {
   })
 
   it ('submits edited tag fields', async () => {
-    tagsApi.fetchTag.mockResolvedValueOnce (buildTag ({ id: 7, name: 'old' }))
-    api.apiPut.mockResolvedValueOnce (buildTag ({ id: 7, name: 'new', aliases: ['alias'] }))
+    const updatedTag = buildTag ({ id: 7, name: 'new', aliases: ['alias'] })
+    tagsApi.fetchTag
+	.mockResolvedValue (updatedTag)
+	.mockResolvedValueOnce (buildTag ({ id: 7, name: 'old' }))
+    api.apiPut.mockResolvedValueOnce (updatedTag)
 
     renderPage ()