fix: chat functionality and extended thinking handling

- bundle/bundle.md: Add provider-anthropic with source URL and orchestrator config override
  to disable extended_thinking (foundation enables it by default, causes empty text
  responses for simple queries)
- Dockerfile: Add amplifier-module-provider-anthropic pip install for container
- backend/agui_adapter.py: Fix thinking block handling and empty text block rendering
  - Thinking blocks no longer fall through to text handler
  - Text blocks only emit START when actual content arrives
  - Handle amplifierd wire format (block_index/block_type, complete text in content_block:end)
- frontend/src/hooks/useChat.ts: Reset assistantId on TEXT_MESSAGE_END to prevent stale
  message IDs across turns
- tests/test_agui_adapter.py: Add extended thinking test coverage

Chat functionality now works end-to-end. Verified: login -> create session -> send message -> receive AI response visible in chat UI.

Generated with Amplifier

Dockerfile

@@ -54,7 +54,8 @@ ENV UV_LINK_MODE=copy
 # amplifierd depends on), so we install it explicitly in the same step.
 # amplifier-core IS on PyPI and will be resolved automatically.
 RUN uv pip install --system \
-    "amplifierd @ git+https://github.com/microsoft/amplifierd"
+    "amplifierd @ git+https://github.com/microsoft/amplifierd" \
+    "amplifier-module-provider-anthropic @ git+https://github.com/microsoft/amplifier-module-provider-anthropic"
 
 # ── Frontend: install deps and build ──────────────────────────────────────────
 # Copy package manifests first so npm ci is cached independently of source changes.