FN-7631: add content search to Chat sidebar with title-only toggle

Chat sidebar search now matches message content by default, not just the conversation title/agent, with an opt-out toggle to restore title-only filtering.

- Add ChatStore.searchSessionsByMessageContent (parameterized LIKE ... ESCAPE) for server-side content search across sessions
- GET /chat/sessions route (register-chat-routes.ts, legacy.ts) gains q/titleOnly query params, debounced server-side content lookup merged with local title/agent matches
- useChat hook exposes searchInTitleOnly state and wires debounced content search into session list results
- ChatView renders a "Search in title only" toggle beside the search box (desktop + mobile) and shows a "Matched: ..." preview snippet on content-matched rows
- Task-planner sessions remain excluded from content matches via the same common-feed visibility guard used for the normal session list
- Add unit/integration tests: chat-store content-search, chat-routes API test, ChatView content-search test
- Update docs/dashboard-guide.md to document the new content search behavior and toggle
- Add changeset fn-7631-chat-content-search.md (@runfusion/fusion minor)

Files changed:
 .changeset/fn-7631-chat-content-search.md          |   7 +
 docs/dashboard-guide.md                            |   2 +
 .../__tests__/chat-store.content-search.test.ts    | 157 +++++++++++++++++++++
 packages/core/src/chat-store.ts                    |  64 +++++++++
 packages/core/src/chat-types.ts                    |   8 ++
 packages/dashboard/app/api/legacy.ts               |  23 ++-
 packages/dashboard/app/components/ChatView.css     |  30 ++++
 packages/dashboard/app/components/ChatView.tsx     |  26 ++++
 .../__tests__/ChatView.autosize.test.tsx           |   2 +
 .../__tests__/ChatView.content-search.test.tsx     | 114 +++++++++++++++
 .../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            | 105 ++++++++++++--
 .../dashboard/src/__tests__/chat-routes.test.ts    |  78 ++++++++++
 .../dashboard/src/routes/register-chat-routes.ts   |  39 ++++-
 packages/i18n/locales/en/app.json                  |   2 +
 packages/i18n/locales/es/app.json                  |   2 +
 packages/i18n/locales/fr/app.json                  |   2 +
 packages/i18n/locales/ko/app.json                  |   2 +
 packages/i18n/locales/zh-CN/app.json               |   2 +
 packages/i18n/locales/zh-TW/app.json               |   2 +
 25 files changed, 667 insertions(+), 12 deletions(-)

Fusion-Task-Id: FN-7631

Fusion-Task-Lineage: bc68b489-26a7-453e-901b-bda816af364e

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

packages/dashboard/app/api/legacy.ts

@@ -10019,11 +10019,30 @@ export interface ChatRoomMessageResponse {
   message: ChatRoomMessage;
 }
 
+/**
+ * FNXC:ChatSearch 2026-07-07-00:00:
+ * `q`/`titleOnly` mirror the server's GET /chat/sessions content-search params (see
+ * register-chat-routes.ts). `q` triggers server-side message-content search; `titleOnly=true`
+ * (or omitting `q`) preserves the pre-existing client-side title/agent-only filtering.
+ */
+export interface FetchChatSessionsOptions {
+  status?: string;
+  q?: string;
+  titleOnly?: boolean;
+}
+
 /** Fetch all chat sessions for a project */
-export function fetchChatSessions(projectId?: string, status?: string): Promise<ChatSessionListResponse> {
+export function fetchChatSessions(
+  projectId?: string,
+  status?: string,
+  options?: FetchChatSessionsOptions,
+): Promise<ChatSessionListResponse> {
   const search = new URLSearchParams();
   if (projectId) search.set("projectId", projectId);
-  if (status) search.set("status", status);
+  const resolvedStatus = options?.status ?? status;
+  if (resolvedStatus) search.set("status", resolvedStatus);
+  if (options?.q && options.q.trim()) search.set("q", options.q.trim());
+  if (options?.titleOnly) search.set("titleOnly", "true");
   const qs = search.toString();
   return api<ChatSessionListResponse>(`/chat/sessions${qs ? `?${qs}` : ""}`);
 }