fix: use gitleaks CLI instead of licensed action, fix lint errors

- Replace gitleaks-action (requires paid license) with direct CLI
  invocation -- same engine, no license needed
- Fix ruff I001 import sorting in voice.py and test_llm.py
- Remove unused imports: _chat_request (test_llm), Path (test_music)
- Remove unused assignment: original_spawn (test_voice)

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

plugins/voice.py

@@ -13,8 +13,8 @@ import json
 import logging
 import threading
 import time
-import wave
 import urllib.request
+import wave
 
 from derp.http import urlopen as _urlopen
 from derp.plugin import command