WinUI control-panel cleanup: grouped cards, default title bar, persisted size

[opariffazman]

What

Streamlines the WinUI control panel for clarity/accessibility.

• Grouped layout — flat single StackPanel → two bordered cards under section headers: Camera (camera, Start/Stop + status, Mirror, Lock-exposure, Exposure) and AI Effects (green screen + Expand/Feather, Eye Contact, AI Sharpness + Quality). AutomationProperties names on Start/Stop + a polite live-region status line.
• Gesture-help InfoBar — surfaces the two non-obvious overlay gestures (scroll-to-resize, drag-the-＋-handle).
• Removed controls — Lock-overlay, Click-through, Zoom. Overlay is now always-interactive + unzoomed. (OverlaySettings fields, HotkeyAction enum members, and OverlayWindow setters intentionally retained — ponytail:-commented — to avoid config-schema churn.)
• Default Windows title bar, titled "Camera On Screen" (no custom chrome).
• Persisted panel size — AppConfig.PanelWidth/Height (physical px), saved on resize (debounced via AppWindow.Changed) + on close, restored next launch. First launch sizes to content.
• Dropped dead ToggleLock/ToggleClickThrough default hotkeys; corrected the VK-code comment.

Design / plan

• Spec: docs/superpowers/specs/2026-06-26-winui-control-panel-cleanup-design.md
• Plan: docs/superpowers/plans/2026-06-26-winui-control-panel-cleanup.md

Verification

• Core unit tests: 59 passing (added a panel-size config round-trip test).
• App build: clean locally against a stub shim — 0 warnings. CI (self-hosted RTX) is the authoritative compile + export-verify gate.
• Human visual gate: confirm grouped cards, default title bar reading "Camera On Screen", the InfoBar hint, absence of Lock/Click-through/Zoom, and that panel size restores across launches. (Effect toggles grey out under the stub shim with no Maxine runtime — expected, unrelated to this change.)

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