feat(rag): RAG scoping and context isolation controls

- Migration 0030: add conversations.rag_project_id (NULL=orphan-only,
  -1=all notes, positive=project), projects.auto_summary and
  projects.summary_updated_at
- Three-value scope semantics thread from build_context() → semantic
  search and keyword fallback via orphan_only + effective_project_id
- Project summarization background job (generate_project_summary,
  backfill_project_summaries) called via Ollama; triggered on project
  update and note saves (debounced 1h); runs at startup
- New LLM tools: search_projects (SequenceMatcher scoring on
  title+description+auto_summary) and set_rag_scope (persists to DB,
  workspace-guarded, emits new_rag_scope in SSE done event)
- execute_tool() accepts conv_id + workspace_project_id; generation_task
  passes both and captures scope changes for SSE done enrichment
- Frontend: Conversation type gets rag_project_id; chat store adds
  ragProjectId computed + updateRagScope(); SSE done handler syncs scope
- ChatView: replace sidebar ProjectSelector with a scope chip pill above
  the input bar, animated dropdown, pulse on model-driven scope change

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/fabledassistant/services/generation_task.py

@@ -208,6 +208,8 @@ async def run_generation(
 
     last_flush = time.monotonic()
     all_tool_calls: list[dict] = []
+    new_rag_scope: object = False  # sentinel; set to int|None when scope changes
+    new_rag_scope_label: str | None = None
 
     try:
         cancelled = False
@@ -280,7 +282,16 @@ async def run_generation(
                                 buf.content_so_far += err_text
                             research_completed = True
                         else:
-                            result = await execute_tool(user_id, tool_name, arguments)
+                            result = await execute_tool(
+                                user_id, tool_name, arguments,
+                                conv_id=conv_id,
+                                workspace_project_id=workspace_project_id,
+                            )
+
+                        # Capture RAG scope change for SSE done event
+                        if result.get("type") == "rag_scope_set" and result.get("success"):
+                            new_rag_scope = arguments.get("project_id")
+                            new_rag_scope_label = result.get("scope_label")
 
                         timing["tools"].append({"name": tool_name, "ms": int((time.monotonic() - t_tool) * 1000)})
                         logger.info("Tool %s result: success=%s", tool_name, result.get("success"))
@@ -352,7 +363,11 @@ async def run_generation(
 
         buf.state = GenerationState.COMPLETED
         buf.finished_at = time.monotonic()
-        buf.append_event("done", {"done": True, "message_id": msg_id, "timing": timing})
+        done_payload: dict = {"done": True, "message_id": msg_id, "timing": timing}
+        if new_rag_scope is not False:
+            done_payload["new_rag_scope"] = new_rag_scope
+            done_payload["new_rag_scope_label"] = new_rag_scope_label
+        buf.append_event("done", done_payload)
 
         # Fire push notification when complete (non-critical, fire-and-forget)
         try: