add frameless transparent always-on-top window options and window.move bridge command

[Railly]

Adds three optional window flags and a new builtin bridge command that
unblock overlay/companion window patterns the current API can't express.
Same primitives as Tauri, Electron, and GTK.

Window options

All default false. Readable from app.zon:

• frameless — NSWindowStyleMaskBorderless
• transparent — clear NSWindow + transparent WKWebView
• always_on_top — NSFloatingWindowLevel + can-join-all-spaces

.windows = .{
    .{ .label = "overlay", .frameless = true, .transparent = true, .always_on_top = true },
},

window.move

const r = await window.zero.invoke("zero-native.window.move", {
  dx: 12, dy: -7, clampToVisibleFrame: true,
});
// r.hitX / r.hitY signal boundary hits

dx/dy are screen-space, Y-down. When the payload omits a selector,
the move targets the window that sent the message (matches Tauri's
setPosition). Boundary clamping is opt-in.

Combined with pointer events, this enables custom drag UX with
velocity, momentum, and edge stops — similar to window.startDragging().

Scope

• macOS only. Linux/Windows backends keep their existing signatures.
• CEF host threads the flags through but stubs them (Chromium
  transparency is a follow-up).
• All flags default to false → backwards compatible.

Tests

zig build test passes on macOS 14 / Zig 0.16. New coverage:

• manifest parser for the three flags + defaults
• bridge dispatch for window.move including source-window fallback
  and clamp/hit reporting through an extended NullPlatform

Happy to split into smaller PRs if preferred.

[vercel]

@Railly is attempting to deploy a commit to the Vercel Labs Team on Vercel.

A member of the Team first needs to authorize it.

[vercel]

Additional Suggestion:

CEF backend (cef_host.mm) is missing the zero_native_appkit_move_window implementation, causing a linker error when building with the chromium web engine.

[vercel]

Additional Suggestion:

CEF backend (cef_host.mm) is missing the zero_native_appkit_move_window implementation, causing a linker error when building with the chromium web engine.

[ctate]

@Railly good call! Can you address these plz?

1. Webview example policy gap: The webview example's builtin_policies array doesn't include zero-native.window.move.

2. Silent CEF transparency no-op: When using the CEF backend, transparent (and the other flags for the main window) are (void)-cast away with no warning. A developer who sets transparent = true in their manifest with CEF will get an opaque window with no indication anything went wrong. Could you add a runtime trace/log warning when these flags are set but unsupported on the active backend?

[Railly]

@ctate Pushed 9828fa8. Both items addressed:

1. Webview policy gap: added zero-native.window.move to builtin_policies.
2. Silent CEF flags: ZeroNativeWarnUnsupportedFlags warns via NSLog when frameless, transparent, or always_on_top are requested on the Chromium backend, covering all three since CEF doesn't honor any of them yet. Went with NSLog for now. If you'd rather route this through the runtime trace sink, lmk and I'll wire it through.

Same commit also fixes the CEF linker issue the Vercel bot flagged (zero_native_appkit_move_window stub in cef_host.mm). Verified locally with zero-native cef install + zig build -Dweb-engine=chromium on examples/hello: pre-fix reproduces undefined symbol: _zero_native_appkit_move_window, post-fix builds clean.

[ctate]

@Railly Thanks for the quick follow-up. Policy gap and CEF linker fix both look good.

Found one more CEF thing while testing: frameless and always_on_top actually seem to work fine on CEF since they're just NSWindow attributes. createWindowWithId already applies them. But the main window path in initWithAppName hardcodes them all to NO, so they only take effect on sub-windows. Could you thread the flags through initWithAppName too?

Related: ZeroNativeWarnUnsupportedFlags warns for all three, but only transparent is genuinely unsupported on CEF (opaque Chromium surface). Worth narrowing that to just transparent. Also, CEF window.move silently no-ops clampToVisibleFrame.

[Railly]

@ctate Nice catches, just pushed this commit: 7c5e737:

• initWithAppName: now takes the three flags and threads them into the main window path.
• ZeroNativeWarnUnsupportedFlags warns only on transparent.
• window.move clamps to NSScreen.visibleFrame in CEF, matching AppKit.

Verified with examples/hello -Dweb-engine=chromium and all three flags set: frameless + always-on-top honored, only the transparent warning fires.