Brush ink, highlighter, and Blender-style image links for annotations

[sounak1125]

What changes

Brush and Highlighter (Draw → Annotate)

• Non-destructive ink items drawn above images and notes; pixels are never touched.
• Tapered, pressure/speed-shaped nib (real pen pressure when available); strokes written together merge into one item.
• Highlighter defaults to yellow with its own colour, and blends multiply + a faint screen pass so text under it stays crisp on light and dark images.
• Cursor previews the nib at its real size and colour.

Arrows

• Tapered shaft, swept head, and a contrast outline so marks read on any image. Shift locks the angle in 15° steps.
• Dragging from one image/note onto a different one makes a link drawn like a Blender node link: square to each edge, spread along shared edges, re-routed every frame so it follows moves, resizes, rotation, undo and reopen.
• Link ends unplug/re-plug by dragging; deleting an item deletes its links (undo restores both). An arrow drawn within one image stays a plain annotation arrow.

Selection bar: colour swatches, thinner/thicker, solid/dotted, arrowheads (end/both/none), contrast outline, each one undo step.

Fix: double-click with an annotation tool, or on an annotation, no longer refits the view.

Behaviour changes

• Existing arrows render in the new style (outline on).
• Annotation tools keep their own screen-relative widths (arrow/brush 3, highlighter 16) instead of sharing the pen width. smoke-image-edit-isolation now asserts the arrow's own 3px width; its intent (never the eraser width) is unchanged.
• Boards saved with ink opened in older versions drop the ink items.

Tests

• scripts/test-annotation-geometry.mjs (in npm test): stroke outlines, taper, link sides/sockets/curves, socket spreading, pressure, halo colour, build wiring.
• scripts/smoke-annotations.mjs (test:annotations-smoke, CI step): real CDP mouse input for writing, highlighter, link create/move/unplug/re-plug/delete+undo, restyle+undo, hit tests, double-tap guard, save/reopen. The double-tap assertion was checked to fail with the guard removed.
• Draw time on the 2,000-item spatial smoke unchanged at 0.29 ms.

🤖 Generated with Claude Code