Server:
- DedupTracker in AppState: bounded HashSet (10,000 IDs, FIFO eviction)
- send_message: extracts message ID from bincode, drops duplicates
- WS handler: dedup on both binary and JSON message frames
- extract_message_id() parses all WireMessage variants
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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