- Intercept fe-navigate events to keep symbol clicks within the
  source viewer instead of navigating to /api/
- Add pushState/popstate for browser back/forward support
- Use fe-code-block with data-scope for field and impl signatures,
  replacing plain <code> tags with SCIP-highlighted code blocks
- Support #src/ hash URLs for bookmarkable source viewer state

- Generated /api docs now inherit the C64 palette and Silkscreen font.
  New web/static/css/api-theme.css overrides the CSS custom properties
  that fe-web now exposes (palette vars, font stacks, weight pinning,
  pixel-smoothing knobs, content-width cap) so the viewer retheme is a
  variable-override exercise rather than a specificity battle.

  Makefile's `docs` target injects the theme link into the generated
  index.html after the baseline stylesheets.

- c64.css: scrollbars blend with the CRT palette via ::-webkit-scrollbar
  and scrollbar-color, responsive breakpoint bumped from 768 to 1024px
  so tablets collapse to single column, mobile root font-size set to
  22px (Silkscreen at smaller rem values was unreadable).

- Source viewer on the landing page is now just the code block. The
  fields/trait-impls render was a half-baked doc page and duplicated
  what /api already presents. Clicking a symbol in the source viewer
  navigates to the full /api doc page in the same tab.

- base.html preconnect swap for the newly imported Press Start 2P and
  Silkscreen bundle (via api-theme.css @import).