roto: video -> take file builder with interactive tuning

Analysis half of the pipeline in docs/roto-puppet.md. Stabilises a face out
of a clip via a similarity fit on rigid landmarks, reduces the lip contour to
a fixed vertex budget, selects sparse keys on velocity minima, and previews
the result as flat indexed fills so timing can be judged without an Animator
Pro render.

- landmarks.js  ordered lip/oval rings; slot position is vertex identity
- mathutil.js   closed-form 2D similarity, Procrustes mean, transform smoothing
- pipeline.js   stabilise -> subsample -> key-select
- raster.js     indexed scanline fill, no antialiasing
- take.js       take-file writer
- selftest.js   29 assertions, incl. ring simplicity at every vertex budget

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

extract.sh

@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+# Extract a clip to a PNG sequence for the take builder.
+#
+# Frames are pre-extracted rather than decoded in the page on purpose: browser
+# video seeking by currentTime is approximate and requestVideoFrameCallback only
+# delivers frames at playback speed, so neither gives a deterministic per-frame
+# pass. A PNG sequence is exact, instantly seekable, and reproducible.
+set -euo pipefail
+
+src="${1:?usage: ./extract.sh CLIP [FPS] [OUTDIR]}"
+fps="${2:-24}"
+out="${3:-frames}"
+
+rm -rf "$out"
+mkdir -p "$out"
+ffmpeg -hide_banner -loglevel warning -i "$src" -vf "fps=$fps" "$out/%04d.png"
+echo "$(ls -1 "$out" | wc -l) frames at ${fps}fps -> $out/"