[Feature] UX discoverability with focus/hover

[Firstp1ck]

Summary: Improve UX discoverability with focus/hover action descriptions.

1) Hover / focus descriptions for buttons

Problem

Icon-only or compact buttons are ambiguous; users want discoverability without reading the wiki.

Recommended implementation

• Primary: On focus, show a one-line description in a status bar or help line (keyboard-first; works in all terminals).
• Secondary: If mouse tracking is enabled and supported, mirror the same string on hover after a short debounce.
• Centralize metadata: extend button/widget definitions with label_short, description, optional keybind_hint so help overlay and inline hints stay in sync.

Acceptance criteria

• Every actionable control in main flows has a description visible via focus or documented alternative.
• No duplicate strings diverging from help overlay.

Testing

• Snapshot or unit test that button registry includes non-empty descriptions for registered actions.