Custom mouse cursor: normal/paint/pipette with recorder-aware software mode

- CursorController: polls painter state in LateUpdate; paint cursor only
  while the brush preview decal actually draws (MeshPainter.BrushPreviewVisible),
  pipette while held/toggled, fallback to normal over UI (InputUtil.PointerOverUi)
- Auto ForceSoftware while Unity Recorder is recording (reflection into
  editor-only assembly, 0.5s poll, editor-only) so the cursor is captured;
  back to hardware cursor when recording stops
- 3 placeholder cursor PNGs (32x32, cursor import type) with per-cursor hotspots

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

Assets/Textures/Cursors.meta

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