Folders over the 50-item cap now show a "Mas..." item that reveals
the next page on tap, instead of silently dropping the rest. Paging
slices the cheap raw list before building any MediaItem, so items
beyond the requested page are never resolved (art, title) -- proven
by a call-count test. Also swaps the raw SAF content:// URI shown in
settings for a parsed, human-readable folder name with a localized
fallback across all 13 locales.
servicio_audio.dart is untouched; this stays entirely within the
local-music tree/dispatch layer.
Phase 1: pick a device folder via SAF (persisted grant, no new
permission), browse its nested subfolders/tracks as a 5th Android
Auto root folder (hidden until configured), and play tracks through
the existing pipeline (EQ, art rotation, cold-start-safe source).
No metadata/sort/filter/shuffle yet -- filename is the title, generic
rotating art is the placeholder; deferred to a follow-up phase.
Adds a new pluriwave/file_actions native method (listAudioChildren)
and an onActivityResult override in MainActivity for the SAF folder
picker -- both static-review-only, no Android build available here.