Polish black-glass WPF surfaces

[aksOps]

What changed

• Refined the shared near-black and champagne glass material system.
• Reworked preview, widget, overlay, settings, and about surfaces for consistent floating translucency and corner radii.
• Removed visual clutter, corrected clipped viewport controls, and improved compact/high-contrast states.
• Made synthetic WPF breakpoint measurement independent of the hosted runner's display width.
• Regenerated the standalone SnipIT.ps1 distribution from the authoritative modular sources.

Why

The initial UI revamp rendered too flat and heavily outlined on real WPF, with some controls clipping at narrower sizes. This pass gives the interface the intended premium floating-glass appearance while keeping interaction behavior unchanged.

The Windows CI runner also caps its hidden test window at 1024 px. The layout test now uses an isolated WPF measurement host so the requested 1200×700 Wide breakpoint is tested deterministically instead of being arranged inside the capped OS window.

Impact

The application change is visual-only. No hotkey, capture, annotation, lifecycle, installation, or dependency behavior changed. The CI correction is confined to the existing -TestAction measurement seam. The generated release remains a single portable PowerShell script with no external runtime dependencies.

Validation

• Deterministic build contract: passed
• Release pure tests: 334/334
• Development pure tests: 334/334
• Release WPF tests: 218/218
• Development preview smoke: 26/26
• AST parse: passed
• PSScriptAnalyzer errors: 0
• Independent UI code review: ready to merge