Switch-over: site chrome and default version to v3.9.1 (hero, nav, sitemap, llms.txt, browse)

[styk-tv]

Problem

The site chrome still announces the previous epoch. The landing hero reads “Protocol v3.7” and all default navigation routes into /v3.7/….

Tasks

• Landing hero: version string and hero actions point at the v3.9.1 set
• Default/versionless doc links route to /v3.9/ (older sets remain reachable)
• sitemap.xml covers the v3.9 pages and ontology files
• llms.txt regenerated against the v3.9.1 set
• Browse index includes the new version
• Feature tiles on the landing page re-checked against v3.9.1 (counts and claims must match the new set, e.g. loop/edge/check enumerations)

Depends on

The v3.9.1 documentation set existing (see the authoring issue in this milestone). This issue is the switch-over, kept separate so the set can be reviewed on the site before it becomes the default.

[styk-tv]

Progress in af10321: the landing page now announces CKP v3.9.1 (Critical Isolation) — CKN notation section, measured epoch timeline v3.4 → v3.10, live artifact surface — and llms.txt / sitemap.xml are aligned. Remaining for this issue: the VitePress doc-set chrome (nav dropdown labels, version switcher badges, default doc routing), which switches when the v3.9.1 set (#2) ships.

[styk-tv]

Shipped. Switch-over complete: the Docs nav and version switcher default to v3.9.1 (current) with v3.10 (in design); the Ontology nav leads with the v3.8 runtime core; llms.txt lists the v3.9.1 set and the verb-vs-query-surface distinction; sitemap.xml and the homepage are refreshed to current versions (pgCK v0.4.17, 33 releases; fleet 58). Older sets remain reachable through the switcher.