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>

js/take.js

@@ -0,0 +1,41 @@
+// Take-file writer. Format is specified in docs/roto-puppet.md, "The take
+// format". Line-oriented text on purpose: Poco can parse it with fopen/fgets
+// from poco/src/safefile.c and strtok/atoi/atof from poco/src/strlib.c, so the
+// Animator Pro render script needs no new native code.
+
+const r = (v) => Math.round(v);
+
+export function writeTake(take) {
+  const L = [];
+  L.push(`take    name=${take.name}  frames=${take.frames}  width=${take.width}  height=${take.height}  exposure=${take.exposure}`);
+  L.push('');
+  take.palette.forEach((p, i) => L.push(`pal     ${i} ${p.name.padEnd(11)} ${i}`));
+  L.push('');
+  // v1 emits a single frozen plate derived from the face oval. A real project
+  // replaces this with hand-drawn angles referenced by cel frame; the record
+  // shape is the same either way.
+  L.push(`plate   0  kind=poly  slot_mouth=${r(take.slot.x)},${r(take.slot.y)}  scale=1.00  rot=0  squash=1.00`);
+  L.push('');
+  for (const part of take.parts) {
+    const bits = [`part    ${part.name.padEnd(9)} kind=${part.kind}  z=${part.z}`];
+    if (part.color !== undefined) bits.push(`color=${part.color}`);
+    if (part.kind === 'poly') bits.push('closed=1 fill=1');
+    bits.push(`interp=${part.interp}`);
+    if (part.parent) bits.push(`parent=${part.parent}`);
+    L.push(bits.join('  '));
+  }
+  L.push('');
+  for (const part of take.parts) {
+    for (const k of part.keys) {
+      if (k.hidden) { L.push(`key     ${part.name.padEnd(9)} f=${k.f}  hidden`); continue; }
+      if (part.kind === 'plate') { L.push(`key     ${part.name.padEnd(9)} f=${k.f}  plate=${k.plate}`); continue; }
+      const pts = k.pts.map((p) => `${r(p.x)},${r(p.y)}`).join(' ');
+      // f is authoritative (what renders); src is the pre-snap extreme frame,
+      // kept only as a tuning signal - a key dragged far means the minimum-hold
+      // and the exposure grid are fighting.
+      L.push(`key     ${part.name.padEnd(9)} f=${k.f}  src=${k.src}  n=${k.pts.length}  ${pts}`);
+    }
+  }
+  L.push('');
+  return L.join('\n');
+}