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

deploy/k8s/base/gateway.yaml

@@ -44,9 +44,6 @@ spec:
         - name: wait-for-dragonfly
           image: busybox:1.36
           command: ['sh', '-c', 'until nc -z dragonfly 6379; do echo waiting for dragonfly; sleep 2; done;']
-        - name: wait-for-qdrant
-          image: busybox:1.36
-          command: ['sh', '-c', 'until nc -z qdrant 6333; do echo waiting for qdrant; sleep 2; done;']
         - name: wait-for-iceberg-catalog
           image: busybox:1.36
           command: ['sh', '-c', 'until nc -z iceberg-catalog 8181; do echo waiting for iceberg-catalog; sleep 2; done;']