content: convert HTML tables to markdown tables and style them

[kbvernon]

Part 3 of 5 — Zola component migration.

1. #N1 chore: fonts and lockfile
2. #N2 fix: scroll-margin
3. #N3 content: markdown tables
4. #N4 feat: Zola components
5. #N5 refactor: get_taxonomy

Merge in order.

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Zola supports pipe tables, so a lot of the clunky machinery I added was unnecessary.

Removes the raw_table and load_table shortcodes ahead of #N4 by converting their consumers to plain markdown tables, and adds a table block to css/content.css so bare markdown tables pick up the basecoat styling the shortcodes used to apply.

• convert all HTML/CSV tables to pipe tables
• cran-msrv.qmd now emits via knitr::kable() instead of building a raw_table shortcode call. MSRV numbers shift because the chunk re-ran against current CRAN data.
• Wraps the R_init_{{{mod_name}}} passage in 06-rextendr-internals in {% raw %} so Zola stops parsing it as template syntax.