enhancement: hook health check / reset button in Settings

[grimmerk]

Add a UI in Settings (Sessions section) to check/reset hook status:

• Show current hook installation status (installed/missing)
• Reset button to re-install hooks if they were removed by another app
• Related to session status hooks (PR feat: session status hooks (working/idle/needs-attention) #92)

Already implemented in PR #92:

• Toggle ON/OFF to enable/disable hooks
• Startup idempotent check (installs if enabled but missing)
• Known limitation: if hooks removed externally while running, restart to recover

Still needed:

• Visual indicator showing hook health status (installed ✓ / missing ✗)
• Manual reset/re-install button (without needing restart)

🤖 On behalf of @grimmerk — generated with Claude Code