Ports app/.../Ansi.kt, Highlighter.kt, Languages.kt and MarkdownSyntax.kt
to client-core, module for module, with every HighlighterTest and
AnsiTest case ported alongside (49 tests total). ansi.rs replaces
Compose's AnnotatedString/SpanStyle with a plain StyledText/Style pair
so the crate stays free of any UI framework, per RUST.md.
cargo test (49 passed), clippy --all-targets and fmt clean.
Co-Authored-By: Claude Sonnet <noreply@anthropic.com>
