fix KV API to unified format, and test

test/README.md

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+# FFmpeg Plugin Tests
+
+Integration tests for the FFmpeg metadata extraction plugin.
+
+## Requirements
+
+Tests require FFprobe to be installed. Since FFprobe is typically only available in the Docker container, tests are designed to run inside Docker.
+
+## Running Tests
+
+### Quick Start (Recommended)
+
+```bash
+# From the plugin directory
+./test.sh
+```
+
+This builds a test Docker image and runs all tests inside it.
+
+### Options
+
+```bash
+./test.sh --no-cache   # Rebuild without Docker cache
+./test.sh --shell      # Start interactive shell for debugging
+```
+
+### Running Locally (if FFprobe is installed)
+
+```bash
+npm install
+npm test
+```
+
+## Test Structure
+
+```
+test/
+├── fixtures/
+│   ├── generate-test-video.sh   # Generates test video files
+│   ├── simple.mp4               # Basic video + audio (generated)
+│   ├── multi-audio.mkv          # Multiple audio tracks (generated)
+│   ├── with-subs.mkv            # Video with subtitles (generated)
+│   └── audio-only.mp3           # Audio file for skip tests (generated)
+├── integration.test.ts          # Integration tests
+└── README.md                    # This file
+```
+
+## Test Categories
+
+### Integration Tests (`integration.test.ts`)
+
+1. **Prerequisites** - Verify FFprobe and fixtures are available
+2. **Manifest** - Validate plugin manifest structure
+3. **Skip Logic** - Test that non-video files are skipped
+4. **FFprobe Validation** - Direct FFprobe output verification
+5. **Output Format** - Validate FFprobe JSON matches plugin expectations
+
+## Test Fixtures
+
+Test fixtures are generated automatically during Docker build using `generate-test-video.sh`. The script creates:
+
+- `simple.mp4` - 2-second 320x240 H.264 video with AAC audio
+- `multi-audio.mkv` - Video with two audio tracks (English + Japanese)
+- `with-subs.mkv` - Video with embedded SRT subtitles
+- `audio-only.mp3` - Audio file (for testing skip logic)
+
+## Writing New Tests
+
+```typescript
+import { describe, it, expect } from 'vitest';
+import path from 'path';
+
+const FIXTURES_DIR = path.join(__dirname, 'fixtures');
+
+describe('My New Test', () => {
+    it('does something', async () => {
+        // Your test here
+    });
+});
+```
+
+## Debugging
+
+Start an interactive shell in the test container:
+
+```bash
+./test.sh --shell
+
+# Inside container:
+npm test                          # Run all tests
+npx vitest run -t "skip"          # Run tests matching "skip"
+ffprobe test/fixtures/simple.mp4  # Manually inspect video
+```