New frontmatter'd docs:
- download (ServeFile — raw bytes, family-lens enforced; corrects the old
download doc's claim that no download route is registered: ServeFile IS
routed, DownloadBook is the dead code)
- set_audio_speed (speed range 0.25-4.0, NaN/Inf rejected)
- rescan (abridged example over the full 70+-column row; write-after-success
guarantee noted)
- purge-archived (destructive, admin), unarchive (204), merge (SHA-256
precondition, per-user collisions keep active copy)
- facets (two modes: facet+values, field autocomplete counts)
- filter_count (family lens)
Registry: RawMessage pins for map/abridged responses; Schema{} for non-JSON
body routes (download = raw bytes; unarchive = 204). Audit now:
missing docs down to ~55 (from 112), 0 orphans.
