fix(#832): retain revoke fence on rejected cycles

docs/scratchpads/832-receipt-challenge-protocol.md

@@ -10,4 +10,4 @@
   3. Implement the broker-minted receipt challenge and exact receipt observation/consume/promote path.
   4. Run unit, framework-shell, compile, lint, and type checks; push after the required queue guard; report to `mosaic-100`.
 - **Risks:** The standalone harness must drive the real daemon without a divergent fixture. If that is impossible, stop and flag Mos.
-- **Evidence:** Initial RED recorded in `/home/hermes/agent-work/reviews/832-wi5-red-receipt-challenge.log`; initial green checks passed. Remediation RED recorded in `/home/hermes/agent-work/reviews/832-wi5-remediation-red.log` before observer/payload implementation: forged `h_source`/`h_payload` was accepted and the observer module was absent. Remediation GREEN: observer/payload/T26/T29 unittest (4 tests), normative-fragments unittest (5), state-store regression (10), full mutator-gate acceptance (20, including the real begin → observer → consume → promote path), `py_compile`, Mosaic package lint/typecheck, and targeted Prettier check. The P5 harness was updated for the test-observer seam but was not fired. Coverage tooling remains unavailable (`python3 -m coverage`: module not installed). Push pending.
+- **Evidence:** Initial RED recorded in `/home/hermes/agent-work/reviews/832-wi5-red-receipt-challenge.log`; initial green checks passed. Remediation RED recorded in `/home/hermes/agent-work/reviews/832-wi5-remediation-red.log` before observer/payload implementation; remediation green passed. Remediation-2 RED recorded in `/home/hermes/agent-work/reviews/832-wi5-remediation2-red.log`: each rejected begin restored prior VERIFIED authority. Remediation-2 GREEN: receipt unittest (5: all `INVALID_CONSTRUCTION`, `PAYLOAD_CONSTRUCTION_REFUSED`, and `PAYLOAD_BINDING_MISMATCH` cases preserve UNVERIFIED and deny the next mutator), normative-fragments unittest (5), state-store regression (10), full mutator-gate acceptance (20, including the real begin → observer → consume → promote path), `py_compile`, Mosaic package lint/typecheck, and targeted Prettier check. The P5 harness remains unfired. Coverage tooling remains unavailable (`python3 -m coverage`: module not installed). Push pending.

packages/mosaic/framework/tools/lease-broker/daemon.py

@@ -303,6 +303,10 @@ class Broker:
     def __init__(self, store: StateStore, observer: ReceiptObserver | None = None) -> None:
         self.store = store
         self.observer: ReceiptObserver = observer if observer is not None else UnavailableReceiptObserver()
+        # Set only by begin_verification after its mandatory revoke-first fence.
+        # It is preserved if later cycle admission is refused; all other broker
+        # actions retain the normal snapshot rollback behavior.
+        self._rejected_cycle_fence: tuple[dict[str, object], dict[str, dict[str, object]]] | None = None
         # VERIFIED authority is deliberately volatile: broker restart revokes all
         # leases while preserving WI-1 identity and pending-token integrity.
         self.leases: dict[str, dict[str, object]] = {}
@@ -391,6 +395,7 @@ class Broker:
             raise StateCommitUncertain()
         previous = copy.deepcopy(self.store.value)
         previous_leases = copy.deepcopy(self.leases)
+        self._rejected_cycle_fence = None
         try:
             response = self._handle(peer, request)
             if self.store.value != previous:
@@ -405,9 +410,18 @@ class Broker:
         except StateCommitUncertain:
             raise
         except Exception:
+            fence = self._rejected_cycle_fence
+            if fence is None:
                 self.store.value = previous
                 self.leases = previous_leases
+            else:
+                # A refused re-verification must never resurrect the preceding
+                # VERIFIED authority. Preserve only this post-revoke fence;
+                # every unrelated partial-write failure still rolls back.
+                self.store.value, self.leases = fence
             raise
+        finally:
+            self._rejected_cycle_fence = None
 
     def _handle(self, peer: tuple[int, int, int], request: dict[str, object]) -> dict[str, object]:
         peer_pid, peer_uid, peer_gid = peer
@@ -473,6 +487,11 @@ class Broker:
                 raise BrokerFailure("INVALID_LEASE_TTL")
             # Revoke-first is a broker operation, not advisory adapter order.
             self.revoke_session_authority(session_id)
+            # If subsequent construction admission rejects, handle() restores
+            # this fence rather than the pre-cycle VERIFIED snapshot.
+            self._rejected_cycle_fence = (
+                copy.deepcopy(self.store.value), copy.deepcopy(self.leases)
+            )
             try:
                 constructed = build_payload_from_wire(construction)
             except ValueError as exc: