v3.7 nav: top-level Ontology dropdown defaults to /ontology/v3.7/

The 'Ontology' nav entry was a dropdown without a default link --
clicking the label could resolve to whichever item the menu state
defaulted to (often v3.6 because of menu ordering or browser cache).

Adds link: '/ontology/v3.7/' to the parent and tags v3.7 as Current
in the dropdown. Older versions remain accessible from the dropdown.

Does not touch any v3.6-page sidebar -- those still scope to v3.6
ontology + earlier (v3.5-alpha6) so v3.6 readers see version-aligned
links.

Author: styk-tv

docs/.vitepress/config.mts

@@ -33,9 +33,10 @@ export default withMermaid(defineConfig({
       },
       {
         text: 'Ontology',
+        link: '/ontology/v3.7/',
         items: [
           { text: 'Browse Ontology', link: '/browse/index.html' },
-          { text: 'v3.7 (TTL)', link: '/ontology/v3.7/' },
+          { text: 'v3.7 (TTL) — Current', link: '/ontology/v3.7/' },
           { text: 'v3.6 (TTL)', link: '/ontology/v3.6/' },
           { text: 'v3.5-alpha6 (TTL)', link: '/ontology/v3.5-alpha6/' },
           { text: 'v3.5-alpha3 (TTL)', link: '/ontology/v3.5-alpha3/' },