[v0.17 READY-B] Make readiness verdicts lease-scoped and observational

[TheGreenCedar]

Source package READY-B in the v0.17.0 consolidated remediation program.

Contract

Deliver W3.3, W3.4, and W3.6: compute strict readiness once per ReadyLease; memoize operation-scoped freshness without weakening same-mtime drift or torn-read guards; cache the canonical-table map by publication; and make status/doctor consume existing lease evidence without scanning, observing, migrating, or repairing.

Parent proof tracker

#1396 remains the protected installed-latency and live-readiness proof tracker. This child owns the remaining source implementation and its deterministic source gates; its PR closes only this child.

Dependencies

READY-A / #1599 and the source-identity order declared by #1179.

Program boundaries

• The implementation PR uses a codex/* branch, targets dev/codestory-next, and carries Closes #N for this child only.
• Status and doctor remain observational. A source cache or responsive process is not installed-runtime proof.
• Preserve content-verified freshness and fail closed on identity or receipt drift.
• Do not touch product version surfaces.

Done when

A warm packet performs exactly one readiness fingerprint pass; same-mtime mutation remains detectable; canonical-table work is publication-keyed; and hostile tests prove status/doctor cannot create observers, scan, migrate, or repair. #1396 stays open for the protected installed measurements.

Refs #1179