Add P2 Knowledge Workspace PageIndex/OpenKB closeout evidence

[yvette-carlisle]

Summary

• add the XY-1066 P2 Knowledge Workspace closeout report and JSON snapshot
• add a changed-source watch/rebuild knowledge fixture with source refs, stale lint, version diff, and reviewable memory-candidate boundaries
• wire the closeout command, docs indexes, runbook, README, and tests while preserving PageIndex/OpenKB as reference-only not_tested rows

Validation

• cargo make fmt
• cargo make lint-fix
• cargo make checks
• cargo make real-world-memory-p2-knowledge-closeout

Boundary

• No claim that ELF beats PageIndex or OpenKB in this closeout.
• No P3 issue is queued by this lane.
• PageIndex/OpenKB remain not_tested until contained adapters emit comparable artifacts.