Sticky UX overhaul — clear separation between card resize and text size:
- S/M/L toggle (12/14/18px) in contextual toolbar for sticky text size
- TransformBox: horizontal-only resize for stickies with live text
reflow during drag (no more stretch-then-snap)
- Hide vertical handles (tc/bc) for sticky-only selections
- Minimum sticky width of 80px enforced in both drag and bake
- TextEditor: sticky background auto-resizes as user types
- textLimits.ts comment corrected to match actual usage
Plain text unchanged: resize gesture scales fontSize via bake.
Fully backward compatible — existing stickies map to nearest preset.