android: the room can measure the song, and a cold artist page stops waiting on one call

The tap-to-sync room draws the recording's own vocal band
(lyrics_vocal_activity, the desktop's coarse envelope) as a strip under the
head, and one button lays every line across the stretches it says are sung —
the desktop's own generator, shared and unit-tested, which refuses rather
than guesses when there is too little voice to read. The result is labelled
an estimate everywhere it shows, the cursor goes back to the top so the taps
correct it, and one more tap drops the whole thing back to an empty set,
because a rough fill stamps every line at once and leaves Undo nothing to
take back. The artist page now fires the hero seed and the overview beside
the full page, the way the desktop stages them: a hero Kyle picked on this
phone comes back off the file with no network at all, the discography paints
from the overview's first page until the exhaustive pass lands with the
classified one, and both lanes are dropped with the page when a hero
changes. ANDROID.md's "Not done yet" is rewritten as the true map of the
port — what is absent by design and why, what is waiting on Rust rather than
on a file picker, and one bullet about the artwork viewer that had been done
for rounds.
