- Enable rd2qmd-core "roxygen" feature to properly convert roxygen2
  markdown code blocks (fixes <div class="sourceCode"> appearing in
  help output for packages like dplyr)
- Handle <br>/<br/>/<br /> inline HTML as line breaks instead of
  literal text
- In table cells, <br> splits into multiple visual rows with proper
  column alignment
- Block-level HTML rendered as plain text lines
- Add tests for br handling in and outside tables

Co-Authored-By: Claude Opus 4.6 <[email protected]>

…onsistency

- Use UnicodeWidthStr::width() instead of byte len() for table column
  width calculation and padding, fixing misalignment with CJK text
- Remove backtick wrapping from inline code in table cells to match
  non-table rendering (both now rely on cyan styling only)

Co-Authored-By: Claude Opus 4.6 <[email protected]>

Extract tokenize_r() as a public API from RTreeSitterHighlighter,
making tree-sitter R tokenization reusable outside the REPL.

The markdown renderer now detects R code blocks (```r) and applies
per-token syntax highlighting using the same tree-sitter-r parser
and color scheme as the REPL input. Non-R code blocks continue to
render with the dim style.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

Add default_code_lang parameter to render_markdown() so callers can
specify a fallback language for fenced code blocks without a tag.

The help pager passes Some("r"), which means \preformatted{} blocks
from Rd (which rd2qmd emits as bare ```) now receive R syntax
highlighting instead of the generic dim style.

Explicit language tags always take precedence over the default.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

- Derive pager colors from RColorConfig::default() via
  nu_ansi_color_to_ratatui instead of hardcoding duplicates
- Unify parser: RTreeSitterHighlighter now uses the shared
  thread-local parse_r() instead of its own RefCell<Parser>
- Replace silent bounds skip with debug_assert in flush_code_block

Co-Authored-By: Claude Opus 4.6 <[email protected]>

Co-Authored-By: Claude Opus 4.6 <[email protected]>

Code blocks in the markdown pager now have a distinct dark background
(Color::Indexed(236)) that spans the full terminal width, making them
visually distinguishable from body text.

The fix has two parts:
- markdown.rs: flush_code_line() sets Line.style bg for code block lines
- mod.rs: render() pads bg-colored lines with spaces to fill full width,
  working around ratatui's Paragraph only applying bg to content width

Co-Authored-By: Claude Opus 4.6 <[email protected]>

flush_code_line() had an early return on empty spans, which caused
blank lines within code blocks to lose their background color. Now
always emit a line with the code block background style, even when
no spans are accumulated.

Co-Authored-By: Claude Opus 4.6 <[email protected]>