fix(api): home agent falls back to multi-project folder manifest when no project_id

app/core/deep_agent.py

@@ -1418,6 +1418,10 @@ async def run_home_stream(
     if project_id:
         manifest = await _fetch_project_manifest(project_id)
         manifest_block = format_folder_manifest(manifest)
+    if not manifest_block:
+        # No specific project context — surface all linked folders so the agent
+        # can answer questions like "tell me about project X" using its files.
+        manifest_block = await build_brief_multi_project_manifest()
     system_prompt = system_prompt + ("\n\n" + manifest_block if manifest_block else "")
 
     trace_id = _trace_id_from_context(prepared_context)