Quality migrations

Display-column measurement

Widget geometry now measures Unicode display columns instead of scalar-value counts. CJK, combining marks, emoji sequences, and regional indicators no longer drift from painted hit regions.

This closes WIDTH-HINT, WIDTH-LIST, WIDTH-STATUS, and WIDTH-ERROR. Consumers need no API change; labels may wrap or reveal horizontal scrolling at different columns when their scalar count differs from their terminal width.

Focused panel styling

Focused panels preserve the established single-line border glyphs and use the semantic focus color for emphasis. Caller style overrides continue to take precedence without changing border geometry.

Typed terminal overlays

This closes RAW-OVERLAYS. Error dialogs expose layout-derived hyperlink regions; consumers decide how and when to emit OSC requests. The raw post-frame byte-vector helper was removed.

Canonical palette adapters

This closes COLOR-LAYERS. Ratatui colors derive from the canonical RGB tokens, and the SVG encoder serializes arbitrary Ratatui RGB values instead of maintaining a second semantic palette table.

Canonical foundation namespaces

Dialog geometry lives in termrock::layout; focus, hover, and modal lifecycle live in termrock::interaction; scroll geometry and rendering live in termrock::scroll; and backdrop policy lives in termrock::widgets::Backdrop. Backdrop::default() provides an opaque terminal-background fill. The entire donor-shaped termrock::components facade is removed so consumers compose the canonical widget API directly.