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

protobuf/tick.proto

@@ -34,6 +34,15 @@ message Tick {
 
   // Additional flags for special trade types
   optional TradeFlags flags = 10;
+
+  // When true: synthetic seed record carrying pre-aggregated OHLC for accumulator init.
+  // price = open (scaled), amount = volume (scaled); seed_* fields carry H/L/C/period.
+  optional bool is_seed = 11;
+  optional int64 seed_high = 12;
+  optional int64 seed_low = 13;
+  optional int64 seed_close = 14;
+  optional uint64 seed_window_start_ms = 15;
+  optional uint32 seed_period_seconds = 16;
 }
 
 message TradeFlags {