FN-7651: remove chat "Search in title only" toggle

Simplifies chat search UX by always matching both title and message content, removing the now-unneeded title-only toggle button and state.

- Removed the "Search in title only" toggle button and its CSS from ChatView
- Dropped searchInTitleOnly/setSearchInTitleOnly state and logic from useChat; content-search query params are now always-on
- Updated ChatView tests to drop title-only toggle interactions and assertions
- Removed the title-only-search i18n string across all locales
- Updated dashboard-guide.md docs to reflect the simplified search behavior
- Added a patch changeset documenting the removal

Files changed:
 .../fn-7651-remove-chat-title-only-toggle.md       |  7 +++
 docs/dashboard-guide.md                            |  4 +-
 packages/dashboard/app/components/ChatView.css     | 18 --------
 packages/dashboard/app/components/ChatView.tsx     | 26 +++--------
 .../__tests__/ChatView.autosize.test.tsx           |  2 -
 .../__tests__/ChatView.content-search.test.tsx     | 51 ++++++----------------
 .../components/__tests__/ChatView.draft.test.tsx   |  2 -
 .../__tests__/ChatView.hash-mention.test.tsx       |  2 -
 .../__tests__/ChatView.mobile-render.test.tsx      |  2 -
 .../components/__tests__/ChatView.rooms.test.tsx   |  2 -
 .../__tests__/ChatView.scroll-to-top.test.tsx      |  2 -
 .../components/__tests__/ChatView.test-harness.tsx |  2 -
 packages/dashboard/app/hooks/useChat.ts            | 39 ++++++++---------
 packages/i18n/locales/en/app.json                  |  1 -
 packages/i18n/locales/es/app.json                  |  1 -
 packages/i18n/locales/zh-CN/app.json               |  1 -
 packages/i18n/locales/zh-TW/app.json               |  1 -
 packages/i18n/locales/ko/app.json                  |  1 -
 packages/i18n/locales/fr/app.json                  |  1 -
 19 files changed, 47 insertions(+), 118 deletions(-)

Fusion-Task-Id: FN-7651

Fusion-Task-Lineage: 5a31825c-8e6e-441f-800d-6053f5f844ba

Co-authored-by: Fusion (runfusion.ai) <noreply@runfusion.ai>

docs/dashboard-guide.md

@@ -511,8 +511,8 @@ Chat view provides project-scoped conversations with agents.
 - Editing is truncate-and-resend, not append: the edited message and everything after it are removed first, then the edited text is sent as a new turn through the normal streaming path — so the resulting transcript looks the same as if you had deleted the old messages and typed the correction from scratch, but in one action.
 <!-- FNXC:TaskDetailPlannerChat 2026-07-07-10:15: Document Planner Chat edit-and-resend and the steering/refinement side-effect decision on discard. -->
 - In task-detail **Planner Chat**, editing an earlier message resumes the conversation from that point exactly as in direct chat. If the discarded turns already triggered task-scoped side effects — a steering comment added via the planner steering tool, or a refinement task created via the planner refinement tool — those **are not reverted**: the steering comment stays on the task and the refinement task stays open, because undoing either is destructive and out of scope for a chat edit. After a successful edit-and-resend, task detail refreshes automatically (so Activity/steering reflects reality), and if the discarded range held one of those confirmations you get an informational toast noting that the earlier change was not undone.
-<!-- FNXC:ChatSearch 2026-07-07-00:00: Document content search + the title-only toggle so users know search now covers message bodies by default, not just titles. -->
-- The Chat sidebar search box matches message **content** by default, not just conversation title/agent — so you can find a past conversation by remembering something that was said in it, even if the title doesn't contain the query. Content matches run as a debounced server-side lookup and are merged with local title/agent matches into the same results list. A **Search in title only** toggle beside the search box restores the original title/agent-only, fully client-side filtering behavior. The toggle is available on both desktop and mobile Chat sidebars and does not appear in the Rooms scope (Rooms already hides search/list). When a session is shown because of a content match, its row shows a subtle "Matched: ..." preview of the matching message so it's clear why the conversation appeared. Task-planner sessions stay excluded from content matches by the same common-feed guard used for the normal session list (see **Settings → Project General → Show task chats in common Chat feed**).
+<!-- FNXC:ChatSearch 2026-07-07-12:00: Content search is always on (FN-7651 removed the "Search in title only" toggle per user request); document the always-on behavior instead of a switchable toggle. -->
+- The Chat sidebar search box always matches message **content** in addition to conversation title/agent — so you can find a past conversation by remembering something that was said in it, even if the title doesn't contain the query. Content matches run as a debounced server-side lookup and are merged with local title/agent matches into the same results list; there is no toggle to restrict search back to title-only. This applies on both desktop and mobile Chat sidebars and does not appear in the Rooms scope (Rooms already hides search/list). When a session is shown because of a content match, its row shows a subtle "Matched: ..." preview of the matching message so it's clear why the conversation appeared. Task-planner sessions stay excluded from content matches by the same common-feed guard used for the normal session list (see **Settings → Project General → Show task chats in common Chat feed**).
 
 ![Chat view](./screenshots/chat-view.png)