fix(gtea): ruff format + check all gtea files and bridge.py

Clears cc-ci self-test lint failures:
- ruff format: 9 files reformatted (all gtea test files + test_discovery.py)
- ruff check --fix: bridge.py UP017 (datetime.UTC alias) + 6 gtea check errors
- manifest.py B007: rename unused loop variable path → _path (no auto-fix available)

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

bridge/bridge.py

@@ -37,7 +37,7 @@ import time
 import urllib.error
 import urllib.parse
 import urllib.request
-from datetime import datetime, timezone
+from datetime import UTC, datetime
 from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
 
 GITEA_API = os.environ.get("GITEA_API", "https://git.autonomic.zone/api/v1")
@@ -82,7 +82,7 @@ GITEA_TOKEN = _read(os.environ["GITEA_TOKEN_FILE"])
 # Shared dedup across the poll + webhook paths: a comment id triggers at most one run.
 _PROCESSED: set = set()
 _PROCESSED_LOCK = threading.Lock()
-_PROCESS_STARTED_AT = datetime.now(timezone.utc)
+_PROCESS_STARTED_AT = datetime.now(UTC)
 
 
 def log(*a):