Two changes to the ear-boundary ground truth, kept deliberately distinct.

#1 was the last GO with an unfinished instruction — PLN said "trim leading
silence tho" without an amount. The amount is now measured rather than
estimated: every sample is EXACTLY zero up to sample 64038 (1.452109 s @
44.1 kHz), and the first audible frame peaks at -28 dBFS. That is a sample-exact
scan, not a threshold and not a detector, which is why it is allowed into a file
whose header forbids detector output. Recorded as start=1.45, keeping a ~2 ms
guard so the first transient cannot be clipped, with the full measurement and
method stored alongside it for audit.

#11 and #12 gain machine PROPOSALS in a new `candidates` block, structurally
separate from `verified` so nothing can be mistaken for a confirmed boundary.
On the two boundaries that also have ear answers, the `takeover` estimate landed
within 0.7 s (#8 2726.25 vs 2726.4, #10 3268.3 vs 3269.0) — which is a reason to
audition takeover first, not a reason to trust it: n=2, on the cases that were
already easy.

#13 and #15 are listed with an explicit NO CANDIDATE and the reason, so a future
reader does not go looking for numbers that cannot exist: zero voting orbits
across three gates and two estimators, because those transitions share their
sounds and a timbral lens is blind to them by construction.