add: add project specification

SPEC.md

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+# videnc-vibe Specification
+
+## Overview
+FFmpeg-based video transcoder for DVD/Blu-ray to SVT-AV1 with automatic metadata fetching.
+
+## Configuration
+
+Config path: `-c` flag or `~/.config/videnc-vibe/config.yaml`
+
+```yaml
+omdb_api_key: "your-key-here"
+
+encoding:
+  dvd:
+    crf: 30
+    preset: 2
+  bluray:
+    crf: 29
+    preset: 3
+
+paths:
+  input: "./input"
+  output: "./output"
+  originals: "./originals"
+  failed: "./failed"
+```
+
+## Flags
+- `-d` : Delete original after successful encode (default: move to originals/)
+- `-c` : Config file path (default: ~/.config/videnc-vibe/config.yaml)
+
+## Input Parsing
+
+Regex patterns:
+- Movie: `tt\d+` → extract IMDB ID
+- Series: `tvm\d+` + `s\d\de\d\d` → extract TVmaze ID + season + episode (both required)
+
+## Media Detection
+
+| Condition | Media Type |
+|-----------|------------|
+| < 600k pixels/frame | DVD |
+| ≥ 600k pixels/frame | Blu-ray |
+
+## Encoding Parameters
+
+### Video
+- Codec: SVT-AV1
+- Pixel format: yuv420p10le
+- Scaling: zscale filter with spline36
+- Preset: 2 (DVD) / 3 (Blu-ray) - configurable
+- CRF: 30 (DVD) / 29 (Blu-ray) - configurable
+- SVT-AV1 params: film-grain=10,film-grain-denoise=1,scd=1,qm-min=4,qm-max=15
+- Deinterlace: bwdif mode 0 if interlaced
+
+### Audio
+- Pipeline: Extract → WAV (48kHz) → Opus (48kHz)
+- FFmpeg libopus is NOT used (poor quality)
+
+## Matroska Tags
+
+### Movie
+| Tag | Source |
+|-----|--------|
+| TITLE | OMDb response |
+| DATE_RELEASED | OMDb response (ISO 8601: YYYY-MM-DD) |
+| IMDBID | Input filename |
+| ORIGINAL_MEDIA_TYPE | DVD or Blu-ray |
+
+### Series
+| Tag | Source |
+|-----|--------|
+| TITLE | TVmaze response (episode name) |
+| COLLECTION | TVmaze response (show name) |
+| SEASON | Parsed from filename |
+| EPISODE | Parsed from filename |
+| DATE_RELEASED | TVmaze response (ISO 8601: YYYY-MM-DD) |
+| IMDBID | TVmaze response |
+| TVMAZE_ID | Custom tag |
+| ORIGINAL_MEDIA_TYPE | DVD or Blu-ray |
+
+## Stream Metadata
+- Preserve language tags per stream
+
+## Output Naming
+
+| Scenario | Filename |
+|----------|----------|
+| Movie with metadata | `{Title}.{IMDBID}.mkv` |
+| Series with metadata | `{ShowName}.S{season}E{episode}.mkv` |
+| No ID match / API fail | `{random}.nometadata.mkv` |
+
+## File Handling
+
+| Outcome | Input file | Output file |
+|---------|------------|-------------|
+| Success | `-d`: delete, else: move to originals/ | move to output/ |
+| Failure | move to failed/ | move to failed/ |
+
+## Logging
+
+- info.log: Human-readable info level
+- error.log: Human-readable error level
+- structured.json: JSON structured logs
+
+## Polling
+- Scan input folder every 10-30 seconds for `.mkv` files
+
+## Commit Message Format
+Use Conventional Commits style:
+- `add:` for new features
+- `fix:` for bug fixes
+- `refactor:` for code restructuring
+- `chore:` for maintenance tasks
+
+Example: "add: add command line argument support"