Add derived-metric pre-flight enumeration to POST-PUSH-PROTOCOL (+ re-ship blast-radius + tx-ordering since 06-11 file rolled back)

Standup item #2 today. Born from BOLT-1293 PR #12406 six-follow-up-commit pattern: each cursor-bugbot round resolved the previous numerator/denominator concern but found the next unenumerated edge. Same scoping-failure shape as tx-ordering (PR #12309) and blast-radius (BOLT-1281 stray file). Also re-ship blast-radius + tx-ordering checklists — the live POST-PUSH-PROTOCOL.md (mtime 2026-06-11) doesn't contain either, despite prior fleet-tasks (20af42ec 2026-06-16, ac9179af 2026-06-17) claiming completion. Substrate is opaque here — the shared-knowledge dir is not git-managed and either rsync rolled back or those edits never landed on this host (fleet-winston-01). Shipping all three together in one edit. Acceptance: POST-PUSH-PROTOCOL.md Phase 1 has 3 subsections after Golden rule: Commit-blast-radius, Tx-ordering, Derived-metric. Next derived-metric / tx-touching / blast-radius-prone PR is the first enforcement.