chore: freeze EventEnvelope v0 byte contract

CHANGELOG.md

@@ -1,5 +1,14 @@
 # Changelog
 
+## V0.7.3 – Envelope Canonicalization
+
+- Added `format` and `schema` to `EventEnvelope` for stable codec/semantics pinning.
+- Renamed `body` → `payload` in the comms event API (server still accepts `body` as an alias).
+- Canonicalization enforced before persistence/broadcast:
+  - Timestamps truncated to RFC3339 UTC `Z` with seconds precision
+  - `payload` object keys recursively sorted (arrays preserve order)
+- `events.jsonl` now stores one canonical `EventEnvelope` per line.
+
 ## V0.7.2 – Communication Layer
 
 ### Unified Event API
@@ -32,7 +41,7 @@
 # Post a note
 curl -X POST http://127.0.0.1:8088/api/events \
   -H "Content-Type: application/json" \
-  -d '{"kind":"note","node_id":"uuid","author":"operator","body":{"text":"Test","severity":"info"}}'
+  -d '{"kind":"note","node_id":"uuid","author":"operator","payload":{"text":"Test","severity":"info"}}'
 
 # Query events
 curl "http://127.0.0.1:8088/api/events?since=2025-01-01T00:00:00Z&kind=note"