No empty state or onboarding when app starts

[fernandomenuk]

Severity: Major

Description

When the app first loads or when all panes are closed, users see a plain black void with no guidance. New users have no way to discover how to create panes, use keyboard shortcuts, or access the command palette (Ctrl+K).

Location

• crates/wmux-app/frontend/index.html (no empty state markup)
• crates/wmux-app/frontend/layout.js (no empty state check after layout refresh)

Suggestion

Show a minimal welcome/empty state with:

• App name and version
• Key shortcuts: Ctrl+K for command palette, Ctrl+A prefix key
• A "Create Workspace" button or prompt
• Brief list of common actions