wip on autotagging

.planning/plans/completed/004-v1.2.1-format-parity.md

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+# 004 — v1.2.1 Format Parity (OGG + WAV)
+
+> Closes the tag-writing format gap: every file YellowJacket plays can also be edited. OGG Vorbis and WAV writers, plus a wsl_v5 lint cleanup. (This was tracked as M001 in the GSD system; S01–S18 in that milestone were just retroactive imports of v1.0–v1.2.)
+
+**Shipped:** 2026-03-21 · **Phases:** 19-21
+
+## What landed
+
+- **Phase 19 — WAV tag writer.** Custom RIFF parser with lenient-read / strict-write behavior. ID3v2 chunk placed at end of file after preserved chunks. Case-insensitive `id3`/`ID3` chunk detection. Existing ID3v2 tags merged so unknown frames written by other tools survive. Read-back uses `bogem/id3v2.ParseReader` (handles cleared tags correctly; dhowden/tag does not).
+- **Phase 20 — OGG Vorbis tag writer.** Custom OGG page parser/writer with MSB-first CRC32 (Go's `hash/crc32` uses incompatible reflected bit ordering, so a precomputed 256-entry lookup table lives in-package). Vorbis Comment serializer with `METADATA_BLOCK_PICTURE` cover art. Raw byte preservation for non-edited entries — avoids corrupting non-UTF-8 tags. Tests use a programmatic fixture builder (no embedded binaries). CRC32 validated against independently computed known vectors (`OggS` → `0x5fb0a94f`, `{1..8}` → `0x7d0f3681`).
+- **Phase 21 — Cleanup.** wsl → wsl_v5 upgrade, all 19 pre-existing warnings fixed.
+
+## Test coverage
+
+- 7 FLAC round-trip tests (pre-existing).
+- WAV round-trip tests covering all 8 text fields + cover art.
+- OGG round-trip tests with CRC32 validation against known vectors.
+- All pass with `-race`.