Add desktop window decoration modes

[smalitobules]

Summary

• add a desktop window decoration mode switch between T3 Code and the system decoration
• add the shared T3 Code top bar, including fullscreen reveal behavior
• rebuild only the window when switching decoration modes so active chats can keep running
• route drag regions and headers through the active decoration mode across desktop platforms

Validation

• bun run fmt
• bun run lint
• bun run typecheck

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Note

Medium Risk
Medium risk because it changes Electron window creation and introduces window rebuild + new IPC/state syncing paths; failures could impact window lifecycle/state or user settings persistence.

Overview
Adds a new desktop “window decoration” setting (DesktopTitleBarMode: t3code vs system) that is persisted to disk and exposed via IPC, with the Electron main process rebuilding the BrowserWindow when the mode changes (preserving bounds/URL and reverting persistence on failure).

Introduces DesktopWindowState + window actions/zoom handling across the bridge, and updates the web UI to render a custom DesktopWindowTopBar (with fullscreen reveal behavior) and to drive drag-region/header behavior via a new useDesktopWindowState/useWindowDecorationMode hook instead of isElectron checks.

Updates Settings to let desktop users switch decoration modes at runtime, and adjusts desktop menu zoom controls to emit window-state updates.

^{Written by Cursor Bugbot for commit 257467c. This will update automatically on new commits. Configure here.}

Note

Add switchable desktop window decoration modes with a custom frameless title bar

• Adds a DesktopTitleBarMode setting ('t3code' | 'system') that controls whether the app uses a custom frameless window or the native OS frame; defaults to 't3code'.
• Implements a custom DesktopWindowTopBar React component with minimize, maximize/restore, and close controls, including fullscreen reveal animation and zoom-aware scaling.
• Switching modes rebuilds the main BrowserWindow at runtime via rebuildMainWindow, preserving window geometry and the active page URL.
• Exposes setTitleBarMode, getWindowState, performWindowAction, and onWindowState over the Electron IPC bridge so the renderer can control and observe window state.
• Adds a Window Decoration selector in Settings, with the selection persisted to disk via an atomic write and restored on next launch.
• Drag regions in ChatView, Sidebar, DiffPanelShell, and route layouts are now conditioned on the active mode and platform instead of a plain isElectron check.
• Risk: mode changes trigger a full window rebuild; if the rebuild fails, the previous mode is restored but a transient blank window may be visible.

^{Macroscope summarized 257467c.}

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[juliusmarminge]

images pls