Promote OpenVox 9.x and OpenFact 6.x to latest

[miharp]

Phase 2 of the major-version cutover in MAINTAINING.md: /openvox/latest/, /openvox-server/latest/, /openvoxdb/latest/, and /openfact/latest/ now serve the 9.x and 6.x collections. bastelfreak confirmed in Slack today that 9.x should be latest. The ecosystem and OpenBolt collections are unchanged.

Part of #456.

Changes

• Repoint the four _<product>_latest symlinks.
• _config.yml: the _latest collections take the 9.x and 6.x navs.
• _data/nav_map.yml: the 9.x and 6.x entries own /latest/; the 8.x and 5.x entries point at their own URL base.
• _data/products.yml: latest: moves to 9x and 6x for the four products. The 8.x and 5.x ref: series stay as they are rather than being frozen at a final tag, because 8.x is still getting security releases and its generated reference pages should keep tracking them. The products.yml header and MAINTAINING.md step 4 now say to freeze once the last maintenance release has shipped.
• _includes/version-banner.html: the banner on 8.x and 5.x pages now reads "no longer the current release" instead of "no longer actively updated". Add a release lifecycle page (which series are current, maintenance, EOL) #503 tracks the lifecycle page that will say how long 8.x is maintained.

Checks

• Drift: all 8.x changes since the 9.x copy points are either already in 9.x (agent environment selection, CLI underscore note, component versions) or deliberately 8.x-only (8.29.0 release notes). Server, OpenVoxDB, and OpenFact 5.x have had no changes since their copies.
• No-redirect check: no page in 8.x or 5.x is missing from 9.x or 6.x, so no /latest/ bookmark 404s. The OpenFact cli and core_facts pages are generated at build time; prod already serves them under /openfact/6.x/.
• rake test:products_data passes. Local jekyll build verified: the /latest/ landing pages are OpenVox 9, OpenVox Server 9, OpenVoxDB 9, and OpenFact 6; the banner renders on 8.x and 5.x pages only; the version picker marks 9.x and 6.x as latest; 9.x canonicals point at /latest/ and 8.x canonicals at /8.x/.
• rake test:links locally reports only the OpenFact cli.html and core_facts.html targets, which are absent until references:all runs in CI.

Follow-ups (listed on #456)

• Ecosystem DevKit pages still use openvox8 in examples (the VoxBox 10.0.0-openvox8.28.1 image tag and BEAKER_PUPPET_COLLECTION: openvox8).
• The 8.x release notes have no pointer to 9.x yet (Add a release lifecycle page (which series are current, maintenance, EOL) #503).
• Cross-product /latest/ links on frozen 8.x pages now land on 9.x docs, as the reference-generation policy intends; authored 8.x pages that link another product's /latest/ may want pinning later.

Assisted by Claude.

[bastelfreak]

Would it be possible to have \n at the end of the line?

[miharp]

That path is a symlink (mode 120000), so git stores the target name as the blob with no trailing newline; GitHub shows the "No newline" marker on every symlink diff. Adding one would make the link point at "_openfact_6x\n", which doesn't exist. The pre-existing _latest symlinks on master look the same.