Layout:
- Add panel-container and session-panel CSS so workspace content
doesn't overlap sidebar
- Session panels use position: absolute to fill workspace area
- Workspace is now flex column for proper empty-state/panel stacking
Terminal:
- xterm.js overrides now target .session-panel in addition to
.terminal-container so terminal fills available space
- Added debounced window resize handler for terminal re-fit
Notifications:
- Rewrote Notifications class to emit .notification-* classes matching
the existing polished CSS (was emitting .toast-* with no CSS)
- Icon is now a small coloured circle badge instead of oversized SVG
Sidebar:
- Fixed class mismatches: sidebar-dot → protocol-indicator,
sidebar-item-sub → sidebar-item-host, sidebar-star → sidebar-item-star
- protocolColour() now returns proto-ssh etc. matching CSS selectors
Other:
- Replaced prompt() in tab rename with custom _inputPrompt modal