docs: keep only reference documentation, archive one-offs

docs/search.md

@@ -28,6 +28,7 @@ Single-value filters (`collectSearchParams()`):
 - `finality` — finality type
 - `format` — format
 - `keyword` — tag/keyword
+- `language` — language
 
 Results are paginated (`limit = 20` default); the **search bar**
 (`app/templates/partials/search-bar.php`) submits a GET form to `/search`.