Finish unifying link rendering across templates

[caugner]

Context

A major link rendering unification landed in 2024-12-16 (commit e547623), centralizing most link rendering into render_internal_link(), render_link_from_page(), and render_link_via_page() in crates/rari-doc/src/html/links.rs.

Current state

Most templates and sidebar rendering use the unified functions. However, several templates still build links inline:

• templ/templs/subpages_with_summaries.rs — internal links without badges
• templ/templs/glossarydisambiguation.rs — internal links without badges
• templ/templs/xsltref.rs — static localized HTML strings
• templ/templs/links/rfc.rs — external IETF links
• templ/templs/webext_all_examples.rs — external GitHub links
• templ/templs/web_ext_examples.rs — external GitHub links
• templ/templs/embeds/live_sample_link.rs — fragment-only links

Assessment

Some of these are reasonable exceptions (external URLs, fragment-only links, static HTML). The internal link cases (subpages_with_summaries, glossarydisambiguation) could potentially use the unified functions.

This is a low-priority cleanup — the current code works correctly.