fix(low): remove dead assistant client fn, keep route as fallback (L7)

Background: askWorkspaceAssistant (POST /workspace/assistant/answer) had no call
site — the UI talks only to the SSE sibling — and was a parallel contract that
could drift from the live stream (CONTRACT-1).

Fix: delete the dead askWorkspaceAssistant client function and drop its now-
unused WorkspaceAssistantResponse import from api.ts.

Decision (surfaced for review): the report also suggested deleting the type and
the backend route. I did NOT, because both are live/contradict the report's
"dead" framing:
  - WorkspaceAssistantResponse is the streaming response shape rendered by the
    live AssistantPanel (and built in useAssistantHistory), so it stays.
  - The backend /assistant/answer route shares the SAME accounted path as the
    stream (one monthly assistant-turn counter) and is pinned by the
    quota / login-required / error-handling suites, so it can't silently drift.
    Per the report's sanctioned alternative I kept it and documented it as a
    tested lockstep fallback rather than deleting it plus its 5 test files
    (out of scope for a Low / would touch core assistant_service).

Test: frontend vitest (33) + tsc + eslint clean; ruff clean on the backend
docstring-only change.

Fixes: L7
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: LEANDERANTONY

backend/routers/workspace.py

@@ -1110,6 +1110,17 @@ def answer_assistant_question(
     payload: WorkspaceAssistantRequestModel,
     auth_tokens=Depends(get_required_auth_tokens),
 ):
+    """Non-streaming assistant answer — retained as a tested fallback (L1/L7).
+
+    The UI talks only to the SSE sibling below; the dead client wrapper
+    (``askWorkspaceAssistant``) was removed. This route is deliberately KEPT
+    rather than deleted (review L7): it shares the SAME accounted code path
+    (``answer_workspace_question`` -> assistant_service, one monthly
+    assistant-turn counter across both routes) and is pinned by the
+    quota / login-required / error-handling suites, so it cannot silently
+    drift from the stream. If a future change makes it a true parallel
+    contract instead of a thin sync mirror, delete it and its tests then.
+    """
     access_token, refresh_token = auth_tokens
     try:
         return answer_workspace_question(

frontend/src/lib/api.ts

@@ -32,7 +32,6 @@ import type {
   WorkspaceHandoffStartResponse,
   AssistantStreamEvent,
   WorkspaceAssistantRequest,
-  WorkspaceAssistantResponse,
   WorkspaceJobDescriptionUploadResponse,
   WorkspaceQuotaResponse,
   WorkspaceResumeUploadResponse,
@@ -607,16 +606,6 @@ export async function getCustomerPortalUrl(): Promise<{ url: string }> {
   });
 }
 
-export async function askWorkspaceAssistant(payload: WorkspaceAssistantRequest) {
-  return request<WorkspaceAssistantResponse>("/workspace/assistant/answer", {
-    method: "POST",
-    headers: {
-      "Content-Type": "application/json",
-    },
-    body: JSON.stringify(payload),
-  });
-}
-
 // ---------------------------------------------------------------------------
 // Streaming assistant: Server-Sent Events client.
 //