fix: let the site search land on cards

The search splits a page at its headings. Emulator cards were titled in
bold and platform systems folded into blocks under one heading, so a
pasted hash opened the top of a page or the systems overview of a
100-block platform page. Each file card is now a level 4 heading kept
out of the table of contents, and each platform system a heading.

Card lines that list other pages (platforms, packs, source citations,
collection paths) leave the search index: 24.7 MB down to 18.1 MB, the
names, hashes and notes still searchable.

wiki/architecture.md

@@ -66,6 +66,16 @@ dist/                    generated packs (gitignored)
 `platforms/`, `emulators/`, `database.json`, and the `wiki/` sources.
 Documentation changes belong in `wiki/` or in the generator.
 
+The site search splits each page at its headings and sends a result to the
+heading above the match. Every file card is therefore a level 4 heading with
+the card's anchor, and every platform system a heading of its own: a hash
+pasted in the search opens that card or that system, not the top of the page.
+Level 4 stays out of the table of contents (`toc_depth: 3`). The lines that
+list other pages (platforms, packs, source citations, collection paths) sit
+in a `data-search-exclude` block, since the browser downloads and indexes the
+whole search index before it shows a first result. File names, hashes, the
+paths an emulator reads and the notes stay searchable.
+
 ## Data flow
 
 ```