feat: search every view that renders text, not only a document

[andiwand]

🤖 Generated with Claude Code

odr.search(), searchNext(), searchPrevious() and resetSearch() shipped
inside document.js, so only a document view had them — a pdf, a plain text
file, an xml source view and an archive listing had no search at all, and a
host's search bar did nothing on any of them.

The search code moves into its own search.js, with the mark rules as
search.css, and every view that renders text writes the pair. It is
format-agnostic: it walks the page's text nodes and knows nothing about how
they got there. The font specimen, image and media views get nothing — a glyph
grid and a <video> have no text to find.

Per view

• pdf — the glyph layer is aria-hidden, which the walker now rejects by
  the subtree, so a hit lands in the text layer only rather than in both. There
  mark takes color:inherit, or the browser's own mark colour would paint
  the layer that is meant to stay invisible, and mix-blend-mode:multiply, or
  an opaque highlight would cover the glyphs it marks. The service also serves
  the two shipped resources now, which it never had to before.
• text — the line-number gutter is aria-hidden for the same reason: the
  numbers are ours, not the file's, and a search for 1 should not find them.
  The editor reads a caret position through a <mark> instead of past it, so
  editing an editable view still lands the change where the caret is while a
  search is active.
• xml — a hit inside a folded <details> opens it. xml/AGENTS.md said
  the view carries no script; it now says its only one is the shared search.
• archive listing — searches the entry paths.

Testing

• html.linked_resources_are_served covers the pdf service too, which is the
  one that had to learn to answer for a shipped resource.
• Search driven from the console in Chrome on all five view kinds: hit count,
  step, reset, the pdf highlight over both text modes, the gutter staying out
  of the results, and an insert through a mark in the text editor.
• Reference output regenerated: every page gains the link and the script,
  document.css/document.js lose what moved out.

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