fix: 12 bug fixes + PointerCapturer + cascade deps (v0.1.29)

[kolkov]

Summary

Comprehensive bug fix release addressing issues from @celer (Linux), @nzanghi-tst (M4 MacBook), @AnyCPU (macOS Intel), and @kolkov.

Bug Fixes (12)

• Outlined button border invisible — transparent fill before stroke caused GPU SDF interference (BUG-SDF-001). Removed from all 4 painters.
• Disabled Outlined border — stroke color was transparent. Changed to DisabledFg.
• Outlined hover overlay — M3 spec 8% primary tint on hover/press. Added to all 4 painters.
• Checkbox clipping (In the examples/hello app the left side of checkboxes is slightly cut off #117) — stroke inset by borderStrokeWidth/2 in all 5 painters.
• Progressbar flicker (Progress bar flickering in examples/gallery #112) — BindToSchedulerFunc with value deduplication.
• Collapsible content leak (Collapsible panel: table/grid rows render at full size during collapse animation #122) — empty CompositorClip stamp when collapsed.
• Scroll artifacts (Incorrect rendering in examples/gallery #111) — damage ring buffer [3]→[4], fill all slots after full render.
• ListView flash (in examples/gallery the list view will flash sometimes #116) — gcOrphanedTextures after UpdateLayerTree.
• M4 MacBook HiDPI (Examples do not look to be rendering correctly on M4 Macbook Pro #123) — deps cascade (gg v0.48.3 HiDPI + SDF fixes).
• macOS LCD text — PlatformProvider detection via App.PlatformProvider() getter (ADR-024).
• Memory leak on SetRoot — ClearCachedScene in UnmountTree + nil hover/capture refs.
• Slider drag (Dragging the slider only works when the mouse is over the slider widget #110) — PointerCapturer (ADR-031) for widget-level mouse capture.

New Features

• PointerCapturer (ADR-031) — type-assertion extension, auto-release on MouseRelease
• App.PlatformProvider() — public getter for LCD detection
• state.BindToSchedulerFunc — generic signal binding with deduplication predicate
• 40+ new tests

Cascade Dependencies

• gg v0.46.11 → v0.48.3 (text scissor #335, zero-alpha SDF BUG-SDF-001, stroke expander, HiDPI)
• gogpu v0.35.0 → v0.39.0 (PlatformProvider ADR-024, app lifecycle ADR-026, macOS menu, key repeat)
• wgpu v0.28.1 → v0.28.7
• gpucontext v0.18.0 → v0.19.0

Issues Closed

Closes #110, closes #111, closes #112, closes #116, closes #117, closes #122

Test plan

• go build ./... — PASS
• go test ./... -count=1 — 56 packages, 0 FAIL
• golangci-lint run --timeout=5m — 0 issues
• Visual: checkbox, slider drag, progressbar, theme switch, collapsible (Windows)
• Visual: Outlined button border visible (all themes)
• CI green (Ubuntu/macOS/Windows)
• Examples do not look to be rendering correctly on M4 Macbook Pro #123 awaiting macOS confirmation from @nzanghi-tst

[codecov]

Codecov Report

❌ Patch coverage is 93.07692% with 9 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
desktop/desktop.go	79.16%	5 Missing ⚠️
app/app.go	33.33%	2 Missing ⚠️
app/window.go	89.47%	1 Missing and 1 partial ⚠️

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