0014. Captions follow the clips

Context

A caption's start and end took composition seconds, and a word: reference on a caption resolved to the word's time in the asset, which is not where the word plays once the clip is trimmed. <Captions src> was documented as generating cues from the transcript and did not. The model computed caption times by hand from the clip placement, and a trim broke them.

Decision

1. A word, shot or silence reference on a <Caption> under <Captions src="asset:x"> means the composition time at which that asset second plays: the first clip or audio on a visible track that plays x and covers the second gives start + (second − in) / speed. A second no clip plays is UNKNOWN_REF. Numbers and marker: references keep their meaning.
2. <Captions src> with no literal <Caption> children generates them in the resolver, from every transcript word the timeline plays, grouped into cues that break at a sentence end, at a pause longer than maxGap, at a clip boundary, or when a cue would pass maxChars or maxDuration. The cues are generated elements (editable: "generated", parent the <Captions>), with words in composition time.
3. The first edit to a generated cue writes all cues into the file as literal children, as patches, then applies the edit. The inverse is caption/setAll with no nodes, which removes the literals so generation resumes. The fold needs nothing new; bake prints generated cues inside their parent, not after it.

Consequences

• A caption is written once and survives every trim of the clip it belongs to. The model writes start="word:12", not start={0}.
• Captions resolve after track placement, in a pass of their own, and the generated nodes are memoised per <Captions> on the plays of their asset, so an unchanged timeline keeps the same placements.
• Multicam cuts still bake as siblings after the generator; cues bake as children. The rule is whether the parent's capabilities list the kind.
• Speed ramps and reversed clips are not followed by captions yet; the mapping uses the clip's constant speed.