feat(agent): Gradio-powered LangGraph agent chat with streaming, tool calls, file upload, conversation persistence

- Gradio 5.50.0 ChatInterface with type='messages' streaming
- LangGraph create_react_agent with InMemorySaver checkpointer
- 4 @tool functions: search_dashboards, get_health_summary, list_environments, get_task_status
- Structured ChatMessage metadata (7 discriminator types: stream_token, tool_start/end/error, confirm_required, confirm_resolved, error)
- HITL resume via second submit() with interrupt_before/Command
- Dual-identity RBAC: service JWT + user JWT for tool calls
- File upload (10 MB limit, pdfplumber/xlsx/JSON parser)
- Conversation persistence via POST /api/agent/conversations/save
- REST API: list, history, archive conversations; multi-tab gate; LLM config
- LLM provider selection via Admin -> LLM Settings (assistant_planner_provider)
- Svelte 5 AgentChatModel with stream event queue, dedup, stream_status watcher
- MarkdownRenderer using svelte-markdown with semantic Tailwind tokens
- ToolCallCard (3 states: executing/completed/failed)
- ConversationList with search, date grouping, infinite scroll
- ConnectionIndicator with Gradio health status
- /agent route with two-column layout
- Vite proxy /api/agent/gradio -> Gradio SSE
- Fixed: not_() SQLAlchemy operator, route collision with _admin_routes
- Fixed: conversation_id -> id normalization, .pyc cache staleness
- Fixed: event.data array parsing (Gradio returns [jsonStr, null])
- Requirements pinned: gradio==5.50.0, pydantic>=2.7,<=2.12.3

frontend/package.json

@@ -23,6 +23,8 @@
     "@sveltejs/vite-plugin-svelte": "^6.2.1",
     "@testing-library/jest-dom": "^6.9.1",
     "@testing-library/svelte": "^5.3.1",
+    "@vitest/coverage-istanbul": "^4.1.8",
+    "@vitest/coverage-v8": "^2.1.8",
     "autoprefixer": "^10.4.0",
     "eslint": "^9.0.0",
     "eslint-plugin-svelte": "^3.0.0",
@@ -36,7 +38,9 @@
     "vitest": "^4.0.18"
   },
   "dependencies": {
+    "@gradio/client": "^1.0.0",
     "date-fns": "^4.1.0",
-    "diff2html": "^3.4.56"
+    "diff2html": "^3.4.56",
+    "svelte-markdown": "^0.4.1"
   }
 }