When the Matrix adapter receives encrypted events it can't decrypt
(MegolmEvent), it now:
1. Requests the missing room key from other devices via
client.request_room_key(event) instead of silently dropping the message
2. Buffers undecrypted events (bounded to 100, 5 min TTL) and retries
decryption after each E2EE maintenance cycle when new keys arrive
3. Auto-trusts/verifies all devices after key queries so other clients
share session keys with the bot proactively
4. Exports Megolm keys on disconnect and imports them on connect, so
session keys survive gateway restarts
This addresses the 'could not decrypt event' warnings that caused the
bot to miss messages in encrypted rooms.
* fix(matrix): harden e2ee access-token handling
* fix: patch nio mock in e2ee maintenance sync loop test
The sync_loop now imports nio for SyncError checking (from PR #3280),
so the test needs to inject a fake nio module via sys.modules.
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Co-authored-by: Cortana <andrew+cortana@chalkley.org>
