fix: enable fullscreen support for all titleBarStyle options

[raymondreaming]

Problem

BrowserWindow.setFullScreen(true) silently fails when titleBarStyle is "hidden". The call completes without error, but the window does not enter fullscreen and isFullScreen() returns false.

This prevents apps using custom window chrome from offering native macOS fullscreen.

const win = new BrowserWindow({
  title: "App",
  url: "https://example.com",
  titleBarStyle: "hidden",
  frame: { x: 100, y: 100, width: 800, height: 600 },
});

win.setFullScreen(true);
console.log(win.isFullScreen()); // false

Root Cause

Traced through package/src/native/macos/nativeWrapper.mm. Three factors combine:

1. createNSWindowWithFrameAndStyle never sets collectionBehavior

The window is allocated with initWithContentRect:styleMask:backing:defer:screen: but setCollectionBehavior: is never called. macOS requires NSWindowCollectionBehaviorFullScreenPrimary for [window toggleFullScreen:nil] to be honored. Without it, AppKit silently drops the call.

2. titleBarStyle: "hidden" removes NSWindowStyleMaskTitled

BrowserWindow.ts maps "hidden" to Titled: false, FullSizeContentView: true. Untitled windows cannot enter fullscreen without explicit collectionBehavior configuration.

3. setWindowFullScreen logic is correct but ineffective

// nativeWrapper.mm ~line 7217
extern "C" void setWindowFullScreen(NSWindow *window, bool fullScreen) {
    dispatch_sync(dispatch_get_main_queue(), ^{
        bool isCurrentlyFullScreen = ([window styleMask] & NSWindowStyleMaskFullScreen) != 0;
        if (fullScreen != isCurrentlyFullScreen) {
            [window toggleFullScreen:nil]; // no-op without fullScreenPrimary
        }
    });
}

The state check and toggle logic are correct. The call is simply ignored at the AppKit level because the window lacks the required collection behavior.

Approaches Investigated

Approach	Result
setFullScreen(true) with titleBarStyle: "hidden"	Silently ignored
styleMask: { FullScreen: true } at creation	Broken layout. NSWindowStyleMaskFullScreen (bit 14) is a read-only state flag, not a configuration option. Setting it at creation produces a corrupted window state with a gray title bar remnant.
Menu item with role: "toggleFullScreen"	Same underlying issue. toggleFullScreen: is ignored regardless of invocation method.
titleBarStyle: "hiddenInset"	Works. Preserves Titled, which allows fullscreen. Serves as a viable workaround but forces native traffic light visibility.

Fix

Set collectionBehavior after window allocation in createNSWindowWithFrameAndStyle:

[window setCollectionBehavior:
    NSWindowCollectionBehaviorFullScreenPrimary |
    NSWindowCollectionBehaviorMoveToActiveSpace];

Applied at creation time rather than lazily in setWindowFullScreen so behavior is consistent across all fullscreen triggers (programmatic API, application menu, native window button).

No API changes. No new configuration. Enables fullscreen for all titleBarStyle values.

Verification

Tested on macOS Sequoia (Darwin 25.3.0, arm64), Electrobun v1.16.0:

Scenario	Before	After
"hidden" + setFullScreen(true)	No-op	Enters native fullscreen
"hidden" + setFullScreen(false)	N/A	Exits correctly
"hidden" + isFullScreen()	Always false	Reflects actual state
"hiddenInset"	Works	No regression
"default"	Works	No regression