fix(verification): keep passed uat results across verifier re-runs

A phase whose human UAT passed could loop forever between execute-phase
and verify-work. A gap-closure plan, or a later phase editing a covered
file, made the report stale; verify-work only recorded a passed UAT
against human_needed; the re-run verifier could not see the UAT file and
re-emitted human_needed; and execute-phase's human_needed branch then
rewrote *-UAT.md with every row back to [pending].

- verification.uat-evidence: recorded UAT rows plus the covered
  implementation files changed since the UAT. The verifier (Step 8b)
  treats a row that passed on unchanged code as verified and re-lists
  only affected rows, each with a retest_reason.
- verification.seed-uat: merges the report's human items into *-UAT.md.
  Existing rows are kept byte-for-byte; a pass is reset only with a
  recorded reason.
- verification.canonicalize-uat: the single human_needed -> passed flip,
  gated on the uat-only row predicate; refuses a stale report.
- verification.status reports stale_reason; init.progress lists every
  executed-but-stale phase in reverify_phases.
- verify-work and progress re-run the verifier themselves for a stale
  report instead of routing to execute-phase; execute-phase records a
  gap-closure checkpoint's UAT answers before dispatching the verifier.

Fail-closed properties are unchanged: a malformed fingerprint and a real
change to covered code still read stale.

Emitted-Drift-Ack-Growth: execute-phase.md — verify_phase_goal gains the gap-closure uat-record pointer and the merge-not-overwrite human_needed branch; the uat template it replaced moved into verification.seed-uat
Emitted-Drift-Ack-Growth: msd-verifier.md — new step 8b pointer to the lazily loaded verifier-uat-evidence reference plus the human_verified frontmatter key
Emitted-Drift-Ack-Growth: progress.md — route v.stale now re-verifies every stale executed phase in place instead of naming one command

agents/msd-verifier.md

@@ -537,6 +537,10 @@ Merge those harvested items into the same human verification list as your own an
 **Why human:** {Why can't verify programmatically}
 ```
 
+## Step 8b: Apply Recorded UAT Evidence
+
+If the phase directory holds a `*-UAT.md`, read and follow `~/.claude/msd-core/references/verifier-uat-evidence.md` before Step 9. A human item whose UAT row already passed on unchanged code is verified by that row and leaves the human verification list; a re-listed row that had passed carries a `retest_reason`. Never re-request a UAT the change did not touch.
+
 ## Step 9: Determine Overall Status
 
 Classify status using this decision tree IN ORDER (most restrictive first):
@@ -722,6 +726,7 @@ coincidental_reliance_items: # Only if a ✓ VERIFIED truth holds incidentally
   - truth: "Observable truth that holds incidentally"
     reason: undeclared-precondition | incidental-ordering | fixture-only
     harden: "Precondition/ordering to declare or enforce"
+human_verified: # Only if Step 8b settled items from *-UAT.md — shape in verifier-uat-evidence.md
 human_verification: # Only if status: human_needed
   - test: "What to do"
     expected: "What should happen"