v0.4.0 — sulcus drawing

Draw sulci as well as ROIs, stored the way pycortex already stores sulci.

Sulci

• A sulcus is an open editable bezier curve. Pick Sulcus in the panel's new ROI | Sulcus selector and drag along the sulcus.
• Export sulci (SVG) writes an overlays.svg-compatible fragment: open, unfilled <path> elements in a sulci layer. quickflat.add_sulci, the WebGL viewer, and Inkscape read it natively.
• Trace each hemisphere separately and give both strokes the same name — they merge into one <g inkscape:label="…"> with a <path> per hemisphere, exactly as pycortex's own CaS is stored.
• Sulci carry no vertex membership, because pycortex stores none (there is no get_sulci_verts; sulci are display geometry).

ROIs are unchanged

Closed bezier, enclosed-vertex membership, and the pycortex-roidraw/vertexset-v2 JSON are byte-for-byte as before. v1/v2 files still import. No format bump.

Fixes

• Stale drag target. Pressing Delete while dragging an anchor or handle left the drag pointing into the pre-splice array: past the end it corrupted the tangent-handle arrays; still in range it silently moved the wrong anchor. Pre-existing — it affected closed ROIs identically.
• An open curve's endpoints are always corners and show a single tangent handle.
• Panel CSS: the segmented control's width/margin resets were inert due to selector specificity.

Internals

core/bezier.js gained open-curve support behind a closed flag rather than a fork. core/roi-model.js → core/shape-model.js (ROISet → ShapeSet, every shape carries a kind). New pure core/svg-export.js. No ViewerAdapter contract change.

Verified against a live pycortex viewer over the Chrome DevTools Protocol: sulcal paths bake with no trailing Z, ROI paths keep theirs, same-named sulci merge, names are XML-escaped, and no sulcus leaks into the ROI JSON. Not yet verified: feeding the exported fragment back through pycortex's svgoverlay.py parser. See TESTING.md.

Suite: 152 JS tests + Python tooling, green.