Ascending the altitude dial and landing on the higher-altitude clip jumped ~3
seconds. A baked morph `transitions/{h}__{l}.mp4` spans src@0 (frac 0) ->
dst@~LOOP_TAIL_S (frac 1) and is scrubbed bidirectionally, but the steady loop
element always seeked LOOP_TAIL_S (3.0s) on landing. Descending lands on dst at
its tail (matches the seek — the s0026 loop-from-tail fix); ascending lands on
src at the morph's HEAD (src@0), so seeking the tail was a 3s jump.
Make the loop landing frame direction-aware: pure `HEFScrub.loopLandFrame(dir,
loopTailS)` returns 0 when ascending, loopTailS otherwise. `loadLoop` takes a
`landFrame`, stores it as `dataset.loopStart`, and the timeupdate/ended wrap
handlers honor it (the base clips are already seamless crossfade-loops, so a
reverse landing wraps [0,dur] cleanly). The settle path lands explicitly on the
direction's frame so a fast ascent never jumps even if the heading clip wasn't
preloaded in time. App-side only — no 154-morph LFS re-bake.
Verify: node unit (loopLandFrame) + a new reverse-landing e2e asserting the loop
anchors at the head (loopStart "0"), and the existing forward "loops from tail"
e2e still green (12/12 altitude-lock).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Per plan Task 2. Adds <audio id=aud-b>; blendAudio(lo,frac) mixes the two
adjacent scale soundtracks by knob fraction (element reuse across crossings so
only the genuinely-new scale reloads); restAudio settles a single scale at rest.
Diagnostic readout now reports whichever element is audible.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Per plan Task 1. position->segment, frac->currentTime, audio gains, and
integer-crossing detection; 9 node --test cases green.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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