split the content package at its seam

content.go had passed FILE_LOC_WARN, which conventions.md treats as the moment to
split rather than a number to ignore: flat until the figure, then split, never
pre-partitioned. content.go now parses bundles and builds permalinks; site.go holds
the indexed site — lookup with language fallback, aliases, Query and Run. The tests
follow the same seam.

No behaviour change, and the test-coupling gate was right to demand the tests move:
its exemption covers comments and whitespace, not code relocated between files,
where an edit could hide.

docs/state.md

@@ -1,6 +1,6 @@
 # State
 
-**Verified against:** `499d107` on 2026-07-30 — update this line every change.
+**Verified against:** `449850c` on 2026-07-30 — update this line every change.
 If this file disagrees with the code, the code is right and this file is a bug.
 
 ## Inventory
@@ -8,7 +8,9 @@ If this file disagrees with the code, the code is right and this file is a bug.
 | File | Purpose | LOC |
 |---|---|---|
 | `go.mod` | module `khosra`; `x/text`, `yaml.v3` direct | 8 |
-| `internal/content/content.go` | site root → bundles: `os.Root` open, walk, frontmatter split, key/lang derivation, NFC, collision drop, key index, language fallback, alias index, URL building | 358 |
+| `internal/content/doc.go` | package comment | 5 |
+| `internal/content/content.go` | bundles: `os.Root` open, walk, frontmatter split, key/lang derivation, NFC, tag slugs, permalink building | 332 |
+| `internal/content/site.go` | the indexed site: lookup with language fallback, aliases, `Query` and `Run`, sections | 191 |
 | `internal/render/render.go` | goldmark, per-kind template sets with site override, `Page`/`List`/`head` | 214 |
 | `internal/render/templates/` | reference theme: `base.html`, `page.html`, `list.html`, `theme.css` (ADR-0026) | — |
 | `internal/web/resolve.go` | URL → (key, lang) or a canonical redirect: language prefix, `/en/…` fork guard, trailing slash | 56 |