14c. A text overlay was one drawtext line sized from the frame height, so a
long text ran off a vertical frame, and a pre-wrapped text was drawn as a
single line because an explicit newline was never a break. `overlays[].fit`
takes none (the default, today's behaviour) | wrap | shrink, and a newline now
breaks whatever the fit. Wrapping emits one drawtext per line, placed as a
single left-aligned block measured from the widest line, rather than letting
each line centre itself ragged. `captions.fit` takes shrink (the default) |
wrap, folding a too-wide row's trailing words onto a new row instead of
shrinking that event -- on a vertical video shrinking can go below readable.
Word order is preserved, so the karaoke highlight still walks the words in the
order they are spoken.

Both fitters now MEASURE the result instead of scaling the size by the width
ratio. Advance is very nearly linear in size, which is why the shortcut looks
right, but hinting rounds each glyph's advance to whole pixels and the error
compounds over a long string: a 95-character line computed to fit at size 8
measured 440 px against a 300 px budget. A test caught it. _fit_size carried
the same assumption and shrink is its default, so it is fixed the same way.

14d. `visuals[].audio_src` names a separate audio-only file -- DASH sites serve
picture and sound as separate streams, so the best video of a clip often has no
audio track and a caller that cannot mux had to skip it. The picture path is
deliberately left alone: stage 3 reuses it as the visual's video, and an
audio-only file there would render a scene with no image. Lengths in
audio_mix="clip" come from whatever carries the sound.

Also: the dialogue tests no longer depend on a TTS model being installed. They
test how a dialogue scene is VALIDATED and say so -- their portraits are inline
"so the test does not depend on what is saved on this install" -- but three of
them failed standalone with 501 "narration needs a TTS model" without reaching
the validation they exercise. Only the inventory is faked, not the check.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014T3rZnLhydX9QqUcfBbqLu