docs: exclude per-skill pages from search, add curator feature page (#17563)

Skill catalog pages (bundled/optional) were drowning out real user-guide
and reference docs in search results. There are ~3100 of them and they
match on almost every generic term.

- Add `ignoreFiles` regexes to docusaurus-search-local for
  `user-guide/skills/bundled/` and `user-guide/skills/optional/`.
  The two human-written catalog indexes (`reference/skills-catalog`,
  `reference/optional-skills-catalog`) remain indexed.
- Add a new feature page `user-guide/features/curator.md` covering the
  curator subsystem merged in #16049 and refined in #17307 (per-run
  reports): how it runs, config, CLI (`hermes curator status/run/pin/
  restore/...`), `.usage.json` telemetry, archival semantics, and
  recovery. Slotted into the Core features sidebar next to Skills.

Search index size dropped from 5822 docs to 2704 in the main section;
`user-guide/features/curator` is indexed.

website/docusaurus.config.ts

@@ -40,6 +40,19 @@ const config: Config = {
         // Disabled: appends ?_highlight=... to URLs (before the #anchor),
         // which makes copy/pasted doc links ugly. Ctrl+F on the page is fine.
         highlightSearchTermsOnTargetPage: false,
+        // Exclude the auto-generated per-skill catalog pages from search.
+        // There are hundreds of them and they dominate results for generic
+        // terms, drowning out the real user-guide / reference docs.
+        // The two human-written catalog indexes (reference/skills-catalog,
+        // reference/optional-skills-catalog) remain indexed.
+        //
+        // Note: ignoreFiles matches `route` (baseUrl stripped, no leading
+        // slash). With baseUrl '/docs/', `/docs/user-guide/skills/bundled/x`
+        // becomes 'user-guide/skills/bundled/x'.
+        ignoreFiles: [
+          /^user-guide\/skills\/bundled\//,
+          /^user-guide\/skills\/optional\//,
+        ],
       }),
     ],
   ],