remove stale submodule refs, clean up legacy dirs, simplify gitignore

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

.gitignore

@@ -8,13 +8,9 @@ __pycache__/
 .venv/
 **/.venv/
 
-# AI tool caches / generated artifacts
-tools/kokoro_coreml/.venv/
-tools/kokoro_coreml/.venv310/
-tools/kokoro_coreml/kokoro-coreml/checkpoints/
-tools/kokoro_coreml/kokoro-coreml/coreml/
-autoaudiobook/.venv/
-autoaudiobook/samples/
+# Standalone tool repos (not part of the app)
+autoaudiobook/
+tools/
 
 # Build outputs
 build/