fix: test DB isolation, Discord recovery, and over-mocked tests

Test data was bleeding into production tasks.db because
swarm.task_queue.models.DB_PATH (relative path) was never patched in
conftest.clean_database. Fixed by switching to absolute paths via
settings.repo_root and adding the missing module to the patching list.

Discord bot could leak orphaned clients on retry after ERROR state.
Added _cleanup_stale() to close stale client/task before each start()
attempt, with improved logging in the token watcher.

Rewrote test_paperclip_client.py to use httpx.MockTransport instead of
patching _get/_post/_delete — tests now exercise real HTTP status codes,
error handling, and JSON parsing. Added end-to-end test for
capture_error → create_task DB isolation.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/integrations/chat_bridge/vendors/discord.py

@@ -134,6 +134,12 @@ class DiscordVendor(ChatPlatform):
             logger.warning("Discord bot: no token configured, skipping start.")
             return False
 
+        # Clean up any stale client/task from a previous failed attempt
+        # so we don't leak background tasks or hold orphaned connections.
+        # Must happen before the import check — the old client could exist
+        # from when discord.py was available.
+        await self._cleanup_stale()
+
         try:
             import discord
         except ImportError:
@@ -163,9 +169,10 @@ class DiscordVendor(ChatPlatform):
                     logger.info("Discord bot connected (%d guilds).", self._guild_count)
                     return True
                 if self._state == PlatformState.ERROR:
+                    logger.warning("Discord bot: entered ERROR state during connection.")
                     return False
 
-            logger.warning("Discord bot: connection timed out.")
+            logger.warning("Discord bot: connection timed out after 15s.")
             self._state = PlatformState.ERROR
             return False
 
@@ -176,6 +183,23 @@ class DiscordVendor(ChatPlatform):
             self._client = None
             return False
 
+    async def _cleanup_stale(self) -> None:
+        """Close any orphaned client/task from a previous failed start."""
+        if self._client and not self._client.is_closed():
+            try:
+                await self._client.close()
+            except Exception:
+                pass
+            self._client = None
+
+        if self._task and not self._task.done():
+            self._task.cancel()
+            try:
+                await self._task
+            except (asyncio.CancelledError, Exception):
+                pass
+            self._task = None
+
     async def stop(self) -> None:
         """Gracefully disconnect the Discord bot."""
         if self._client and not self._client.is_closed():