(CODUX-119) Restore the Electron title bar UI

[numnx]

🧩 Task: Restore the Electron title bar UI

Automated task PR opened by Code UX for T02.

📋 Summary

Sprint: Sprint 187 · Fix System Bar · Task: T02

Restore the Electron desktop system bar so it is visible in the app, shows the Code UX version, exposes an update action, and reliably supports maximize/restore by double-clicking the bar.

🤖 Model & Provider

Provider	Codex CLI
Model	gpt-5.5

⏱️ Timing

Started	2026-07-08 13:01:45 UTC
Finished	2026-07-08 13:10:20 UTC
Duration	8m 35s

📊 Token Usage

Metric	Value
Input tokens	83,252
Cached input tokens	2,116,992
Output tokens	17,242
Total tokens	2,217,486
Invocations	1
Tool calls	60
Active time	8m 9s

Included usage estimate (subscription/local login): $1.99

✅ QA Review

⏳ QA review runs after this PR is opened. Check the task card in the dashboard for the outcome once it lands.

📝 Full Task Prompt

## Objective
Update the renderer `TitleBar` so the Electron desktop app always shows the system bar when the desktop window API is present, includes the version number and update button, and supports maximize/restore from double-clicking the bar.

## Scope
- Edit `dashboard/src/v2/components/TitleBar.tsx`
- Create `tests/dashboard/v2/title-bar.test.tsx`
- Relevant symbols: `TitleBar`, `__APP_VERSION__`, `window.codeUxDesktop`, `CodeUxWindowApi.toggleMaximize`, `CodeUxWindowApi.onStateChange`, `CodeUxWindowApi.getState`
- Consumes the `window.codeUxDesktop.openUpdates()` bridge added by T01

## Implementation Requirements
1. Keep `TitleBar` desktop-only by returning `null` when `window.codeUxDesktop?.window` is unavailable, but render the full bar whenever that window API exists.
2. Preserve the current logo and `v{__APP_VERSION__}` display, and add a compact `Update` control in the title-bar chrome that calls `window.codeUxDesktop.openUpdates()` when clicked.
3. Ensure all interactive controls are marked as no-drag regions and do not trigger the title-bar double-click handler.
4. Implement double-click maximize/restore through `windowApi.toggleMaximize()` for the non-interactive title-bar area, and update local maximize state from both the returned result and `onStateChange` events.
5. Preserve platform behavior: keep native macOS traffic-light spacing and hide custom window buttons on `darwin`; keep minimize/maximize/close buttons on Windows/Linux/other platforms.
6. Add focused Preact tests that mock `window.codeUxDesktop`, stub `__APP_VERSION__`, assert the version and update button render, assert update click calls the bridge, assert double-click toggles maximize, and assert the maximize button label/icon state updates after state changes.

## Constraints
- Do not render the title bar in normal browser dashboard sessions.
- Do not remove or bypass the existing preload bridge contract.
- Do not add external UI libraries; use existing Preact, Tailwind, and `lucide-preact` patterns.
- Keep text compact enough for the `h-9` system bar and preserve accessible labels for all icon controls.
- Do not break existing rounded Electron shell styling or macOS traffic-light spacing.

## Verification
- Run `pnpm run test:dashboard -- tests/dashboard/v2/title-bar.test.tsx`.
- Run `pnpm run typecheck:dashboard`.
- Success means the mocked Electron title bar shows Code UX, the app version, an update action, working window controls, and double-click maximize/restore without rendering in non-Electron mode.

🌿 Branch Info

Base: feature/CODUX-187-fix-system-bar
Head: task/feature-codux-187-fix-system-bar-t02-codex-mrc37cmo

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🤖 Generated by Code UX