fix: bind cross-role handoff consume role to authenticated profile (Closes #843)

Review #515 F1: gitea_adopt_workflow_lease trusted a caller-supplied role
((role or active_role)), so any namespace holding gitea.read could consume
an author-only cross-role handoff by passing role="author".

- Derive the adopter role authoritatively from the active profile; reject
  any supplied role that does not exactly match (no silent accept).
- Pass the profile-derived role and authoritative profile/namespace context
  to lease_lifecycle.adopt_lease; validate handoff provenance
  required_profile/required_namespace against it (fail closed).
- Fail closed when the profile role cannot be derived (no author default).
- Add MCP-boundary regression tests: reviewer/merger profiles cannot
  consume an author handoff via role="author"; the legitimate author
  profile still consumes; foreign required_profile rejected.

lease_lifecycle.py

@@ -564,8 +564,17 @@ def adopt_lease(
     expected_head_sha: str | None = None,
     owner_pid: int | None = None,
     operator_authorized: bool = False,
+    adopter_profile_name: str | None = None,
+    adopter_namespace: str | None = None,
 ) -> dict[str, Any]:
-    """Sanctioned adopt path with provenance; never silent foreign steal."""
+    """Sanctioned adopt path with provenance; never silent foreign steal.
+
+    #843 F1: for a pending cross-role handoff, ``role`` must be the
+    authoritative profile-derived role supplied by the MCP boundary — never
+    caller-asserted authority. When the handoff provenance declares
+    ``required_profile`` / ``required_namespace`` and the caller context is
+    provided, both are validated exactly; a mismatch fails closed.
+    """
     state = db.get_lease_workflow_state(lease_id)
     if not state:
         raise LeaseLifecycleError(
@@ -607,6 +616,30 @@ def adopt_lease(
                 f"required={required} adopter={adopter_role or 'none'} "
                 "(fail closed)"
             )
+        # #843 F1: provenance profile/namespace restrictions are validated
+        # against the authoritative caller context when declared. Caller
+        # input can never widen authority; a mismatch fails closed.
+        handoff_prov = handoff.get("provenance") or {}
+        required_profile = str(
+            handoff_prov.get("required_profile") or ""
+        ).strip()
+        if required_profile and adopter_profile_name is not None:
+            if str(adopter_profile_name).strip() != required_profile:
+                raise LeaseLifecycleError(
+                    f"wrong profile for cross-role handoff consume of "
+                    f"{lease_id}: required_profile={required_profile} "
+                    f"adopter_profile={adopter_profile_name} (fail closed)"
+                )
+        required_namespace = str(
+            handoff_prov.get("required_namespace") or ""
+        ).strip()
+        if required_namespace and adopter_namespace is not None:
+            if str(adopter_namespace).strip() != required_namespace:
+                raise LeaseLifecycleError(
+                    f"wrong namespace for cross-role handoff consume of "
+                    f"{lease_id}: required_namespace={required_namespace} "
+                    f"adopter_namespace={adopter_namespace} (fail closed)"
+                )
         reason = "cross-role-handoff-consume"
     elif freshness["freshness"] == "active" and not same_owner:
         raise LeaseLifecycleError(