fix(check): line_unread names the captions track that exempts a caption - #7703

Context: I've been using HyperFrames every day for the past two weeks to make Korean Shorts and long-form videos, and it's been great to work with. This PR is one of a batch of fixes for things I ran into along the way, so you'll see several PRs from me at once — sorry for the pile-up, and thanks for your patience. Each one is reproduced on current main, independent of the others, and can be reviewed, merged or closed on its own.

What

The line_unread message now says how to exempt a caption timed to speech: put data-track-kind="captions" on its clip or host. The captions reference now says that check skips that track.

Why

A caption timed to speech cannot stay on screen longer than its words take. A voice-synced Short whose captions were plain clips (<div class="cap clip" data-start … data-track-index="2">) got a line_unread warning on almost every caption line, tens per video:

"만오천 원 정도 받은 것 같아요" (6 words) is on screen 1.67 s (±0.01 s), under its 1.72 s floor: hold it about 0.5 s + 0.3 s a word (2.30 s here) before it leaves or changes; see references/motion.md.

check already skips text under data-track-kind="captions" (isCaptionsText in layout-audit.browser.js). That exemption was only mentioned in a sentence under the craft table in docs/packages/cli.mdx. The message pointed only at holding the line longer, which the voice timing does not allow. caption_track_kind_missing does not help here either, because it only looks at sub-composition hosts.

Related work

• No open issue or PR (searched line_unread captions, craft).
• text_below_floor already offers its opt-out (data-layout-ignore) in its message. This brings line_unread in line with it.

How

• packages/cli/src/utils/craftAudit.ts: both line_unread messages (mid-film and the film's last line) end with …, or, if it is a caption timed to speech, put data-track-kind="captions" on its clip or host so this check skips it; see references/motion.md.
• skills/hyperframes/references/captions.md: the captions-track bullet says check does not time its lines against the reading floor. Skills manifest regenerated.

Test plan

• New unit test names the captions track as the way to exempt a caption timed to speech fails on main and passes with the fix. craftAudit.test.ts: 28 passed.
• Real CLI on a five-caption repro (hyperframes check --no-cache --json):
  • main: 4 line_unread warnings, and the messages do not mention captions.
  • this branch: the same 4 warnings, each naming data-track-kind="captions".
  • Following the hint (the same file with data-track-kind="captions" on each .cap clip): 0 craft findings, on main too.
• oxlint, oxfmt, comment ratchet, fallow audit, typecheck (pre-commit).

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