Agentic UI: Let the app window shrink to 420px

[shaunandrews]

Related issues

None (split out of the stu-2162-site-header-actions exploration)

How AI was used in this PR

Claude Code cherry-picked this change out of a larger exploration branch and verified it (lint, typecheck) in isolation.

Proposed Changes

View ▸ Reload / Force Reload / Toggle DevTools used Electron's role-based "focused webContents" target. With a site preview visible, clicking into the preview would shift focus to the guest page, so Reload reloaded the site preview instead of the app — leaving no way to reload the Studio renderer itself from the menu.

These menu items now target the app window's webContents explicitly, and are relabelled "Reload App" / "Force Reload App" to make that explicit. In agentic mode, Reload App drops its ⌘R accelerator so ⌘R still reloads the preview (the renderer's own "Reload preview" shortcut); Force Reload App keeps ⌘⇧R.

Testing Instructions

1. Launch the app with a site preview visible.
2. Click into the preview area to give the guest webview focus.
3. Use View ▸ Reload App and confirm the app renderer reloads (not the site preview/guest page).
4. In agentic mode, press ⌘R and confirm it still reloads the preview, not the app window.
5. Use View ▸ Force Reload App and confirm it force-reloads the app renderer (⌘⇧R still works too).
6. Use View ▸ Toggle DevTools and confirm DevTools opens for the app window, regardless of which webview had focus.

Pre-merge Checklist

• Have you checked for TypeScript, React or other console errors?