Expand local-only firmware README, add check_si4684_blobs.py to verify gitignore and clean history, and gate main with a new si4684-blobs workflow job. Co-authored-by: Cursor <cursoragent@cursor.com>
Introduces Si4684/ADAU1701 drivers, TunerService, FrequencyKHz, SeekDirection, /api/tuner routes without file-scope globals, host tests, and firmware blob tooling (binaries remain gitignored). Co-authored-by: Cursor <cursoragent@cursor.com>