Fixes#221 - SQLite Memory Override bug.
This PR resolves memory overwrite behavior in autosave paths by replacing fixed memory keys with unique keys, and improves short-horizon recall quality in channel runtime.
**Root Cause**
SQLite memory uses a unique constraint on `memories.key` and writes with `ON CONFLICT(key) DO UPDATE`.
Several autosave paths reused fixed keys (or sender-stable keys), so newer messages overwrote earlier conversation entries.
**Changes**
- Channel runtime: autosave key changed from `channel_sender` to `channel_sender_messageId`
- Added memory-context injection before provider calls (aligned with agent loop behavior)
- Agent loop: autosave keys changed from fixed `user_msg`/`assistant_resp` to UUID-suffixed keys
- Gateway: Webhook/WhatsApp autosave keys changed to UUID-suffixed keys
All CI checks passing.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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