Add custom title bar for Windows

[lintowe]

Summary

• Adds the custom Windows title bar and finalizes it's behavior for desktop

What Changed

• Added/refined the Windows custom title bar behavior across desktop routes
• Updated chat title bar behavior for the final Windows header UX
• Kept configurable title-bar context support for non-chat surfaces

Screenshots

• Before (without custom title bar)

• After (with custom Windows title bar)

Testing

• bun fmt
• bun lint
• bun typecheck

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Note

Medium Risk
Changes desktop window chrome on Windows to a frameless window and routes minimize/maximize/close through new IPC APIs, which can impact basic window behavior across platforms if miswired. UI updates are mostly conditional to Windows Electron but touch shared layout/header code paths.

Overview
Adds a custom Windows title bar for the Electron desktop app by making Windows windows frameless (frame: false) and introducing DesktopTitleBar/DesktopWindowControls in the web UI.

Exposes new window-control IPC in the desktop main/preload layers (minimize, toggleMaximize, close, plus get/onWindowState) backed by a new DesktopWindowState contract, and wires Windows-only title bar rendering into chat, diff panel, settings, and index routes while keeping existing drag-region headers for non-Windows Electron. Also tweaks desktop sidebar header padding on Windows to account for the new chrome.

^{Reviewed by Cursor Bugbot for commit 8865c0e. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Add custom title bar with window controls for Windows desktop

• Adds a frameless window on Windows (frame: false) with a new DesktopTitleBar and DesktopWindowControls component replacing the native title bar
• Exposes minimize, toggle-maximize, close, and window-state IPC channels in main.ts and preload.ts via new DesktopWindowState contracts
• Integrates DesktopTitleBar into ChatView, DiffPanelShell, settings, and index routes on Windows Electron; non-Windows Electron retains existing drag-region headers
• Adjusts sidebar left padding on Windows desktop to account for the removed native controls
• Behavioral Change: on Windows, the native window frame is removed entirely; all window control interactions now go through IPC

^{Macroscope summarized 8865c0e.}

[macroscopeapp]

Approvability

Verdict: Needs human review

This PR introduces a new Windows-specific custom title bar feature with new UI components, IPC handlers, and cross-cutting changes to multiple existing components. While well-scoped to Windows platform, it introduces new user-facing capability and new renderer-main process communication patterns that warrant human review.

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[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 2be07d2. Configure here.}

[cursor]

Close handler fallback may close wrong window

Medium Severity

The resolveEventWindow helper, used by window IPC handlers, includes a fallback to mainWindow or any other active window if the event sender's window cannot be resolved. For the CLOSE_WINDOW_CHANNEL handler, this fallback can cause an unrelated window to close, risking unexpected data loss.

 

^{Reviewed by Cursor Bugbot for commit 2be07d2. Configure here.}

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