fix(fonts): markdown prose + links honour the live UI font (T-475)

The markdown span builders are context-free statics, so they pinned the
bundled clideUiFamily const and ignored the Appearance UI-font setting —
Claude's conversation prose stayed on the default face regardless of the
pick. Thread the resolved UI family through the same ClideMarkdownHooks
carrier already used for mono (T-472): build() resolves it from context and
every prose/link span reads hooks.ui. Adds a regression test asserting prose
and inline code follow the families from the ClideSettingsScope.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -22,6 +22,11 @@ heading, and (b) bumping `pubspec.yaml` `version:` in the same commit.
 
 ### Fixed
 
+- **Markdown prose honours the UI-font setting.** Claude's conversation prose
+  and inline links render through the markdown engine, which pinned the bundled
+  UI face and ignored the Appearance UI-font pick; it now follows the setting
+  live, like the rest of the app. (T-475)
+
 ## [2.7.0] — 2026-06-17
 
 ### Added