docs: record workspace typed core merge

[yha9806]

Summary

• Record platform PR [codex] Add case review labeling CLI #45 / merge commit 530ecb8 as the Workspace typed core foundation merge.
• Update review-context changelog, source index, durable Workspace status, production persistence spec, release-readiness gate, manifest, and M5 closeout.
• Preserve the boundary that typed core foundation is not product-level R5 release readiness.

Gates

• python3 docs/review-context/gates/validate_review_context.py
• python3 -m json.tool docs/review-context/MANIFEST.json >/tmp/vulca-manifest.jsoncheck
• python3 -m json.tool docs/review-context/release-readiness/m5-closeout-summary.json >/tmp/vulca-m5-summary.jsoncheck
• git diff --check
• git diff --cached | gemini-agent diff-review --stdin