Phase 2: Core transcription pipeline and audio playback

- Implement faster-whisper TranscribeService with word-level timestamps,
  progress reporting, and hardware auto-detection
- Wire up Rust SidecarManager for Python process lifecycle (spawn, IPC, shutdown)
- Add transcribe_file Tauri command bridging frontend to Python sidecar
- Integrate wavesurfer.js WaveformPlayer with play/pause, skip, seek controls
- Build TranscriptEditor with word-level click-to-seek and active highlighting
- Connect file import flow: prompt → asset load → transcribe → display
- Add typed tauri-bridge service with TranscriptionResult interface
- Add Python tests for hardware detection and transcription result formatting

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

python/tests/test_transcribe.py

@@ -0,0 +1,51 @@
+"""Tests for transcription service."""
+
+from voice_to_notes.services.transcribe import (
+    SegmentResult,
+    TranscriptionResult,
+    WordResult,
+    result_to_payload,
+)
+
+
+def test_result_to_payload():
+    """Test converting TranscriptionResult to IPC payload."""
+    result = TranscriptionResult(
+        segments=[
+            SegmentResult(
+                text="hello world",
+                start_ms=0,
+                end_ms=2000,
+                words=[
+                    WordResult(word="hello", start_ms=0, end_ms=500, confidence=0.95),
+                    WordResult(word="world", start_ms=600, end_ms=2000, confidence=0.92),
+                ],
+            ),
+        ],
+        language="en",
+        language_probability=0.98,
+        duration_ms=2000,
+    )
+
+    payload = result_to_payload(result)
+
+    assert payload["language"] == "en"
+    assert payload["duration_ms"] == 2000
+    assert len(payload["segments"]) == 1
+
+    seg = payload["segments"][0]
+    assert seg["text"] == "hello world"
+    assert seg["start_ms"] == 0
+    assert seg["end_ms"] == 2000
+    assert len(seg["words"]) == 2
+    assert seg["words"][0]["word"] == "hello"
+    assert seg["words"][0]["confidence"] == 0.95
+
+
+def test_result_to_payload_empty():
+    """Test empty transcription result."""
+    result = TranscriptionResult()
+    payload = result_to_payload(result)
+    assert payload["segments"] == []
+    assert payload["language"] == ""
+    assert payload["duration_ms"] == 0