fix(MAT-258): blacklist unverified E2EE devices + add CI tests

Unverified devices (lacking cross-signing) caused OlmUnverifiedDeviceError
in _send_text(), silently breaking all message delivery. Now on_sync()
blacklists non-cross-signed devices instead of skipping them, and
_send_text() catches E2EE errors gracefully.

Adds 12 unit tests for device trust policy and send error handling.
CI test job now gates deployment in deploy.yml.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

bot.py

@@ -41,6 +41,7 @@ from nio import (
     KeyVerificationMac,
     ToDeviceError,
 )
+from nio.exceptions import OlmUnverifiedDeviceError
 from nio.events.to_device import UnknownToDeviceEvent
 from nio.crypto.attachments import decrypt_attachment
 from livekit import api, rtc
@@ -1515,7 +1516,8 @@ class Bot:
                         self.client.verify_device(device)
                         logger.info("Cross-sign-verified device %s of %s", device.device_id, user_id)
                     else:
-                        logger.debug("Skipped unverified device %s of %s (no cross-signing sig)", device.device_id, user_id)
+                        self.client.blacklist_device(device)
+                        logger.info("Blacklisted unverified device %s of %s (no cross-signing sig)", device.device_id, user_id)
 
     async def on_reaction(self, room, event: ReactionEvent):
         """Handle reaction events for pipeline approval flow."""
@@ -3583,16 +3585,21 @@ class Bot:
             return None
 
     async def _send_text(self, room_id: str, text: str):
-        await self.client.room_send(
-            room_id,
-            message_type="m.room.message",
-            content={
-                "msgtype": "m.text",
-                "body": text,
-                "format": "org.matrix.custom.html",
-                "formatted_body": self._md_to_html(text),
-            },
-        )
+        try:
+            await self.client.room_send(
+                room_id,
+                message_type="m.room.message",
+                content={
+                    "msgtype": "m.text",
+                    "body": text,
+                    "format": "org.matrix.custom.html",
+                    "formatted_body": self._md_to_html(text),
+                },
+            )
+        except OlmUnverifiedDeviceError as e:
+            logger.error("E2EE send failed in room %s: unverified device — %s", room_id, e)
+        except Exception as e:
+            logger.error("Send failed in room %s: %s", room_id, e)
 
     async def _get_call_encryption_key(self, room_id: str, sender: str, caller_device_id: str = "") -> bytes | None:
         """Read E2EE encryption key from call.member state (MSC4143) or timeline (legacy).