[FEATURE]: Escape key should focus the prompt input field in Desktop (follow-up to #30887) #44243

Describe the enhancement you want to request

This is a follow-up to #30887, which was closed as not planned. The underlying gap remains unaddressed in OpenCode Desktop 1.18.21: there is still no quick keyboard shortcut that reliably returns focus to the prompt composer from anywhere in the app.

When focus is elsewhere (message list, sidebar, after interacting with dialogs), you have to click the composer with the mouse before typing. A single Escape press focusing the prompt input — as in Codex Desktop — would make this much smoother.

Related current bug reports showing how often focus ends up stranded (being filed separately by me):

• Composer loses keyboard focus when switching session tabs
• Ctrl+L sometimes fails to restore composer focus

Desired behavior: Pressing Escape in OpenCode Desktop moves focus to the prompt input field regardless of where focus currently is.

Environment: OpenCode Desktop 1.18.21, Microsoft Windows 11 Education 25H2