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/PostEditForm.test.tsx

@@ -1,13 +1,11 @@
-import { act, fireEvent, screen, waitFor } from '@testing-library/react'
-import { beforeEach, describe, expect, it, vi } from 'vitest'
+import { fireEvent, screen, waitFor } from '@testing-library/react'
+import { describe, expect, it, vi } from 'vitest'
 
 import { textContentOf } from '@/test/text'
 import PostEditForm from '@/components/PostEditForm'
 import { buildPost, buildTag } from '@/test/factories'
 import { renderWithProviders as render } from '@/test/render'
 
-import type { DialogueAPI } from '@/lib/dialogues/useDialogue'
-
 const postsApi = vi.hoisted (() => ({
   updatePost: vi.fn (),
 }))
@@ -20,27 +18,18 @@ const toastApi = vi.hoisted (() => ({
   toast: vi.fn (),
 }))
 
-const dialogue = vi.hoisted (() => ({
-    confirm: vi.fn<DialogueAPI['confirm']> (),
-    choice: vi.fn () }))
-
 vi.mock ('@/lib/posts', () => postsApi)
 vi.mock ('@/lib/api', () => api)
 vi.mock ('@/components/ui/use-toast', () => toastApi)
 vi.mock ('@/lib/dialogues/useDialogue', async importOriginal => ({
-    ...await importOriginal<typeof import ('@/lib/dialogues/useDialogue')> (),
-    default: () => dialogue }))
+  ...await importOriginal<typeof import ('@/lib/dialogues/useDialogue')> (),
+  default: () => ({
+    choice: vi.fn (),
+  }),
+}))
 
 describe ('PostEditForm', () => {
-  beforeEach (() => {
-    vi.resetAllMocks ()
-  })
-
   it ('submits edited post fields with the current base version', async () => {
-    const confirm = vi.fn<(value: boolean) => void> ()
-    dialogue.confirm.mockReturnValueOnce (new Promise<boolean> (resolve => {
-      confirm.mockImplementation (resolve)
-    }))
     const onSave = vi.fn ()
     const post = buildPost ({
       id:        8,
@@ -66,16 +55,6 @@ describe ('PostEditForm', () => {
     fireEvent.change (parentIds, { target: { value: '3 4' } })
     fireEvent.submit (screen.getByRole ('button', { name: '更新' }).closest ('form')!)
 
-    expect (postsApi.updatePost).not.toHaveBeenCalled ()
-    expect (dialogue.confirm).toHaveBeenCalledTimes (1)
-    const difference = textContentOf (
-	dialogue.confirm.mock.calls[0][0].description)
-    expect (difference).toContain ('oldnew')
-    expect (difference).toContain ('23 4')
-    expect (difference).not.toContain ('general-tag')
-
-    await act (async () => { confirm (true) })
-
     await waitFor (() => {
       expect (postsApi.updatePost).toHaveBeenCalledWith (
           expect.objectContaining ({
@@ -92,28 +71,6 @@ describe ('PostEditForm', () => {
     expect (textContentOf (toastApi.toast.mock.calls[0][0].description)).toBe ('更新しました．')
   })
 
-  it ('keeps edited fields without submitting when confirmation is cancelled', async () => {
-    const onSave = vi.fn ()
-    dialogue.confirm.mockResolvedValueOnce (false)
-    render (<PostEditForm post={buildPost ()} onSave={onSave}/>)
-
-    const [title, parentIds] = screen.getAllByRole ('textbox')
-    fireEvent.change (title, { target: { value: 'new' } })
-    fireEvent.change (parentIds, { target: { value: '3 4' } })
-    const button = screen.getByRole ('button', { name: '更新' })
-    fireEvent.submit (button.closest ('form')!)
-
-    await waitFor (() => {
-      expect (button).toBeEnabled ()
-    })
-    expect (dialogue.confirm).toHaveBeenCalledTimes (1)
-    expect (postsApi.updatePost).not.toHaveBeenCalled ()
-    expect (onSave).not.toHaveBeenCalled ()
-    expect (toastApi.toast).not.toHaveBeenCalled ()
-    expect (title).toHaveValue ('new')
-    expect (parentIds).toHaveValue ('3 4')
-  })
-
   it ('preserves duration while the video tag is temporarily removed', () => {
     const post = buildPost ({
       videoMs: 180_500,
@@ -143,7 +100,6 @@ describe ('PostEditForm', () => {
       'shows deduplicated original-created endpoint errors on the shared datetime field',
       async () => {
     const post = buildPost ()
-    dialogue.confirm.mockResolvedValueOnce (true)
     api.isApiError.mockReturnValue (true)
     postsApi.updatePost.mockRejectedValueOnce ({
       response: {

frontend/src/components/PostEditForm.tsx

@@ -15,7 +15,7 @@ import { msToTime } from '@/lib/utils'
 import { useValidationErrors } from '@/lib/useValidationErrors'
 import { useUITranslation } from '@/lib/useUITranslation'
 
-import type { FC, FormEvent, ReactNode } from 'react'
+import type { FC, FormEvent } from 'react'
 
 import type { Post, TagWithSections } from '@/types'
 
@@ -23,8 +23,6 @@ type PostFormField =
     'parentPostIds' | 'tags' | 'videoMs'
     | 'originalCreatedAt' | 'originalCreatedFrom' | 'originalCreatedBefore'
 
-type PostEditData = Omit<Parameters<typeof updatePost>[0], 'id'>
-
 const groupedMessages = (...values: (string[] | undefined)[]): string[] =>
     [...new Set (values.flatMap (value => value ?? []))]
 
@@ -152,63 +150,12 @@ const PostEditForm: FC<Props> = ({ post, onSave }) => {
   const handleSubmit = async (e: FormEvent) => {
     e.preventDefault ()
 
-    if (disabled) return
-
     setDisabled (true)
     try
     {
-      const current: PostEditData = {
-	  title, tags, parentPostIds,
-	  duration: videoFlg ? duration : null,
-	  originalCreatedFrom, originalCreatedBefore }
-      const fields: {
-	  [Key in keyof PostEditData]-?: {
-	      name: ReactNode
-	      prev: PostEditData[Key] } } = {
-	  title: { name: label ('shared:labels.title'), prev: post.title },
-	  parentPostIds: {
-	      name: label ('shared:labels.parentPosts'),
-	      prev: (post.parentPosts ?? []).map (parent => parent.id).join (' ') },
-	  tags: { name: label ('tags:title'), prev: tagsToStr (post.tags) },
-	  duration: {
-	      name: label ('shared:labels.duration'),
-	      prev: videoMsToDurationValue (post.videoMs) },
-	  originalCreatedFrom: {
-	      name: <>{label ('shared:labels.originalCreatedAt')}{' '}
-			{label ('shared:labels.since')}</>,
-	      prev: post.originalCreatedFrom },
-	  originalCreatedBefore: {
-	      name: <>{label ('shared:labels.originalCreatedAt')}{' '}
-			{label ('shared:labels.before')}</>,
-	      prev: post.originalCreatedBefore } }
-      const differences = (Object.keys (fields) as (keyof PostEditData)[])
-	  .map (key => ({ key, name: fields[key].name,
-	      prev: fields[key].prev ?? '', current: current[key] ?? '' }))
-	  .filter (row => row.prev !== row.current)
-
-      if (!(await dialogue.confirm ({
-	  title: label ('shared:actions.diff'),
-	  confirmText: label ('shared:actions.update'),
-	  description: (
-	      <dl className="max-h-[60dvh] overflow-y-auto space-y-3 text-left">
-		{differences.map (row => (
-		    <div key={row.key}>
-		      <dt className="font-semibold">{row.name}</dt>
-		      <dd className="whitespace-pre-wrap break-words">
-			{row.prev && (
-			    <del className="block text-red-600 dark:text-red-400">
-			      {row.prev}
-			    </del>)}
-			{row.current && (
-			    <ins className="block text-green-700 dark:text-green-400">
-			      {row.current}
-			    </ins>)}
-		      </dd>
-		    </div>))}
-	      </dl>) })))
-	return
-
-      await update ({ id: post.id, ...current },
+      await update ({ id: post.id, title, tags, parentPostIds,
+		      duration: videoFlg ? duration : null,
+		      originalCreatedFrom, originalCreatedBefore },
 		    { baseVersionNo: post.versionNo })
     }
     finally

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 ()