chore: vendor tool-cache action, retire GARM label vocabulary

[rldyourmnd]

Summary

• Vendor actions/tool-cache/ byte-identical to NDDev-Archive/github-actions-garm@468af475 (verified via git blob SHA). The archived dependency cannot receive fixes; the live copy now sits beside the workflow that runs it — same pattern as the ci-feedback vendoring shipped in 0.1.21.
• private-security-bundle-free.yml: four uses: repointed to ./actions/tool-cache.
• catalog/tools.yml: drop the nddev-tool-cache third-party entry (now a same-repository call, outside registry scope); cache-contract.yml producer renamed to the local path; capabilities.yml records the vendoring provenance.
• Retired GARM label vocabulary (nddev-linux-standard, -untrusted, -integration) replaced by the live nddev-linux label in docs/03, examples/nddev/security-private-selfhosted.yml, and the docker-build/deny_runner comments; ADR-0004 records the 2026-09-17 official-runner cutover as a dated amendment.

Permissions diff

None — no workflow permissions touched.

Threat model

The vendored composite action runs identical bytes to the previously pinned archived action; the trust-scoped cache assignment and checksum-verified upstream fallback are unchanged. Same-repository ./ resolution binds the action to the workflow's own commit — strictly stronger than a cross-repository SHA pin.

Test plan

• validate_all.py --tier core: OK (all 48 checks)
• actionlint: clean
• zizmor@1.26.1 --persona pedantic with token: no findings
• generate_docs.py: rendered output unchanged