feat(slider): implement infinity dragging using PointerLock API

[claygeo]

Summary

Closes #204

Saw this was on your radar @Aymericr — figured I'd take a crack at it since the PointerLock pattern already exists in first-person-controls.tsx.

Slider controls now use the Pointer Lock API for drag interactions. When dragging a slider label, the cursor locks and movement continues infinitely past the screen edge, matching the behavior in Unity3D and other professional 3D editors.

Changes

packages/editor/src/components/ui/controls/slider-control.tsx — 1 file, ~40 lines changed

Before	After
setPointerCapture + e.clientX	requestPointerLock + e.movementX
Drag stops at screen edge	Drag continues infinitely
Cursor visible during drag	Cursor hidden (locked)

How it works

1. Pointer down → requestPointerLock() locks the cursor and hides it
2. Pointer move → accumulates e.movementX (relative delta, not viewport-bound)
3. Pointer up → document.exitPointerLock(), cursor reappears at original position
4. Escape key → pointerlockchange listener cleans up drag state gracefully

Edge cases handled

• PointerLock denied: falls back to setPointerCapture (existing behavior)
• Escape during drag: pointerlockchange listener catches this, commits the value, resumes undo tracking
• Shift/Ctrl modifiers: still work (10x / 0.1x step multiplier)
• Undo/redo: temporal state paused/resumed correctly on all exit paths

Reference

Adapted from the existing PointerLock usage in first-person-controls.tsx (lines 50-64) which uses the same API for camera mouse look.

Test plan

• Drag slider label past screen edge — value keeps changing
• Release mouse — cursor reappears, value commits
• Press Escape during drag — drag cancels cleanly
• Shift+drag — 10x step multiplier still works
• Ctrl+drag — 0.1x step multiplier still works
• Click value to edit — text input still works (not affected)
• Scroll wheel on label — still works (not affected)