feat: add @tag model override support and remove Qdrant dependencies

- Add model-tags parser for @Tag syntax in chat messages
- Support Anthropic models (Sonnet, Haiku, Opus) via @tag
- Remove Qdrant vector database from infrastructure and configs
- Simplify license model config to use null fallbacks
- Add greeting stream after model switch via @tag
- Fix protobuf field names to camelCase for v7 compatibility
- Add 429 rate limit retry logic with exponential backoff
- Remove RAG references from agent harness documentation

sandbox/Dockerfile

@@ -48,6 +48,7 @@ COPY --from=builder /build/env /opt/conda/envs/dexorder
 # Copy application code
 COPY dexorder/ /app/dexorder/
 COPY main.py /app/
+COPY environment.yml /app/
 
 # Copy generated protobuf code from builder
 COPY --from=builder /build/dexorder/generated/ /app/dexorder/generated/