fix(macos): emit the content rect for WINDOW_FRAME events

[iAmCorey]

Symptom

On a multi-display setup (built-in Retina + external monitor), dragging a window to the other display and back leaves the bottom of the canvas clipped — a UiApp's bottom status-bar disappears. Clicking another app and back (key-window change), or manually resizing, heals it. Single-display apps can also hit it intermittently.

Root cause

The macOS host's WINDOW_FRAME event carried window.frame — the outer frame, one titlebar (~32pt) taller than the content area. Everything else in the pipeline speaks content-rect:

• windows are created with initWithContentRect:
• the runtime's shellBoundsForWindow uses the event's size as the shell-view layout viewport (window_frame_changed → relayoutShellViews)
• the window state store round-trips the saved frame back into initWithContentRect:

So every window_frame_changed relayouts shell views to the outer-frame height (the fill gpu_surface gets frame={{0,-32},{560,592}} inside a 560-tall contentView — bottom 32pt clipped), and every RESIZE event snaps them back to the content height. The two events fight continuously; whichever lands last wins. Instrumented log of an idle app:

updateDrawableSize changed scale=2.0 bounds={560, 560} frame={{0, 0}, {560, 560}}
updateDrawableSize changed scale=2.0 bounds={560, 592} frame={{0, -32}, {560, 592}}
updateDrawableSize changed scale=2.0 bounds={560, 560} frame={{0, 0}, {560, 560}}
... (oscillates every frame)

Dragging across displays reliably parks the war on the clipped side; a key-window change parks it on the correct side — which made the bug masquerade as a multi-display issue.

Separately, restore_state windows grow by one titlebar height per launch (outer frame saved, restored as a content rect).

Fix

• emitWindowFrameForWindowId: now emits [window contentRectForFrameRect:window.frame], matching the content-rect semantics of window creation, shell layout, and state restore.
• Add the missing windowDidChangeScreen: / windowDidChangeBackingProperties: delegate re-emits (mirroring windowDidBecomeKey:) so crossing displays refreshes geometry immediately instead of at the next key-window change.

Verification

Dual-display MacBook (built-in Retina @2x + external monitor): before, dragging across displays clipped the bottom 32pt of a zig-core UiApp's canvas; after, layout is stable across display moves, focus changes, and resizes, and the per-frame relayout oscillation is gone.

🤖 Generated with Claude Code

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[vercel]

On macOS, emitWindowFrameForWindowId: reports contentRectForFrameRect: (frame minus titlebar) which under-reports the height of NSWindowStyleMaskFullSizeContentView windows (titlebarStyle 1/2), so WINDOW_FRAME disagrees with the RESIZE event's contentView.bounds and reintroduces the shell-layout oscillation/bottom-clipping for hidden-inset windows.