feat(codex-lens): add unified reranker architecture and file watcher

Unified Reranker Architecture:
- Add BaseReranker ABC with factory pattern
- Implement 4 backends: ONNX (default), API, LiteLLM, Legacy
- Add .env configuration parsing for API credentials
- Migrate from sentence-transformers to optimum+onnxruntime

File Watcher Module:
- Add real-time file system monitoring with watchdog
- Implement IncrementalIndexer for single-file updates
- Add WatcherManager with signal handling and graceful shutdown
- Add 'codexlens watch' CLI command
- Event filtering, debouncing, and deduplication
- Thread-safe design with proper resource cleanup

Tests: 16 watcher tests + 5 reranker test files

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

codex-lens/tests/test_watcher/test_events.py

@@ -0,0 +1,103 @@
+"""Tests for watcher event types."""
+
+from __future__ import annotations
+
+import time
+from pathlib import Path
+
+import pytest
+
+from codexlens.watcher import ChangeType, FileEvent, WatcherConfig, IndexResult, WatcherStats
+
+
+class TestChangeType:
+    """Tests for ChangeType enum."""
+    
+    def test_change_types_exist(self):
+        """Verify all change types are defined."""
+        assert ChangeType.CREATED.value == "created"
+        assert ChangeType.MODIFIED.value == "modified"
+        assert ChangeType.DELETED.value == "deleted"
+        assert ChangeType.MOVED.value == "moved"
+    
+    def test_change_type_count(self):
+        """Verify we have exactly 4 change types."""
+        assert len(ChangeType) == 4
+
+
+class TestFileEvent:
+    """Tests for FileEvent dataclass."""
+    
+    def test_create_event(self):
+        """Test creating a file event."""
+        event = FileEvent(
+            path=Path("/test/file.py"),
+            change_type=ChangeType.CREATED,
+            timestamp=time.time(),
+        )
+        assert event.path == Path("/test/file.py")
+        assert event.change_type == ChangeType.CREATED
+        assert event.old_path is None
+    
+    def test_moved_event(self):
+        """Test creating a moved event with old_path."""
+        event = FileEvent(
+            path=Path("/test/new.py"),
+            change_type=ChangeType.MOVED,
+            timestamp=time.time(),
+            old_path=Path("/test/old.py"),
+        )
+        assert event.old_path == Path("/test/old.py")
+
+
+class TestWatcherConfig:
+    """Tests for WatcherConfig dataclass."""
+    
+    def test_default_config(self):
+        """Test default configuration values."""
+        config = WatcherConfig()
+        assert config.debounce_ms == 1000
+        assert ".git" in config.ignored_patterns
+        assert "node_modules" in config.ignored_patterns
+        assert "__pycache__" in config.ignored_patterns
+        assert config.languages is None
+    
+    def test_custom_debounce(self):
+        """Test custom debounce setting."""
+        config = WatcherConfig(debounce_ms=500)
+        assert config.debounce_ms == 500
+
+
+class TestIndexResult:
+    """Tests for IndexResult dataclass."""
+    
+    def test_default_result(self):
+        """Test default result values."""
+        result = IndexResult()
+        assert result.files_indexed == 0
+        assert result.files_removed == 0
+        assert result.symbols_added == 0
+        assert result.errors == []
+    
+    def test_custom_result(self):
+        """Test creating result with values."""
+        result = IndexResult(
+            files_indexed=5,
+            files_removed=2,
+            symbols_added=50,
+            errors=["error1"],
+        )
+        assert result.files_indexed == 5
+        assert result.files_removed == 2
+
+
+class TestWatcherStats:
+    """Tests for WatcherStats dataclass."""
+    
+    def test_default_stats(self):
+        """Test default stats values."""
+        stats = WatcherStats()
+        assert stats.files_watched == 0
+        assert stats.events_processed == 0
+        assert stats.last_event_time is None
+        assert stats.is_running is False