Mission Run Overview
Mission Run: Placement-Port Residuals Closure
Close the five placement-port safety residuals deferred from PR #2920 so PRIMARY/COORD write-routing correctness is enforced by the port, not coincidental.
PR #2920 hardened the coordination write/read placement port but its review squad deferred five follow-ups as too risky to fold in-PR. This mission closes them: it routes the sole status_phase writer through the port with a fail-closed home-equality check, narrows an over-broad architectural gate carve-out to per-file justified entries, removes a silent PRIMARY-data-loss path in the legacy runtime cutover, unifies three divergent write-target degrade implementations into one helper, and guards a best-effort tracer read against a deleted-coordination-branch crash.