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>

tests/conftest.py

@@ -104,10 +104,14 @@ def clean_database(tmp_path):
         except Exception:
             pass
 
-    # Redirect task queue and work orders DBs to temp dir
+    # Redirect task queue and work orders DBs to temp dir.
+    # IMPORTANT: swarm.task_queue.models also has a DB_PATH that writes to
+    # tasks.db — it MUST be patched too, or error_capture.capture_error()
+    # will write test data to the production database.
     for mod_name, tmp_db in [
         ("dashboard.routes.tasks", tmp_tasks_db),
         ("dashboard.routes.work_orders", tmp_work_orders_db),
+        ("swarm.task_queue.models", tmp_tasks_db),
     ]:
         try:
             mod = __import__(mod_name, fromlist=["DB_PATH"])