fix(desktop-window): apply bidirectional frameless/titlebar updates and clear progress bar correctly

[ndonkoHenri]

• Fixes desktop window state update handling in WindowService so toggles behave correctly across repeated changes.
• Frameless: handle both transitions (false -> true and true -> false) instead of only enabling frameless once. (fix page.window_frameless=False does not restore window chrome after frameless mode #2802)
• Title bar buttons visibility: apply title_bar_buttons_hidden updates even when title_bar_hidden itself does not change.
• Progress bar: allow clearing window.progress_bar by handling None/null transitions and sending native clear value (-1).

Summary by Sourcery

Improve desktop window state handling to correctly apply frameless, title bar visibility, and progress bar updates across repeated state changes.

Bug Fixes:

• Ensure frameless window mode can be both enabled and disabled, restoring standard window chrome when frameless is turned off.
• Apply title bar button visibility updates even when the overall title bar hidden flag does not change, keeping button state in sync with window state.
• Allow clearing the window progress bar by handling null transitions and mapping them to the native clear value.

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[Copilot]

Pull request overview

Improves desktop window state synchronization in WindowService to correctly apply repeated updates for frameless mode, title bar visibility/buttons visibility, and progress bar clearing.

Changes:

• Track and apply title_bar_buttons_hidden updates independently of title_bar_hidden changes.
• Make frameless handling bidirectional (enable and disable).
• Allow clearing the native progress indicator by translating null progress to -1.

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[Copilot]

When disabling frameless mode, the restore path uses titleBarHidden ?? false, which can incorrectly force the title bar to become visible if titleBarHidden is omitted (null) but _titleBarHidden was previously true. Use the already-computed effective/cached state (e.g., _titleBarHidden ?? false) instead of defaulting to false so toggling frameless doesn’t unexpectedly change the title bar visibility.

Suggested change

	// Restore non-frameless window chrome
	await setWindowTitleBarVisibility(
	titleBarHidden ?? false,
	titleBarButtonsHidden,
	// Restore non-frameless window chrome using cached state
	await setWindowTitleBarVisibility(
	_titleBarHidden ?? false,
	_titleBarButtonsHidden,

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