feat(policy): govern delegation and review escalation

docs/POLICY_DECISION_PROVENANCE.md

@@ -130,3 +130,18 @@ bounded outcome counts in audit evidence.
 The shared core WebUI helper `PolicySourcePath` renders the source path shape
 for module UIs. Modules may use their own field layout, but the data contract
 should remain this shape.
+# Function assignment delegation and escalation
+
+The `policy.functionAssignmentGovernance` decision includes the effective
+`delegation_allowed`, `maximum_delegation_depth`, and
+`maximum_delegated_validity_days` values plus zero or more per-step escalation
+rules. Each rule binds `holder`, `authority`, or `recipient` review to one exact
+target function and a bounded timeout. Consumers must treat the decision as a
+current limit, not a captured grant: IDM rechecks it across the complete source
+chain at every consequential transition.
+
+An elapsed timeout does not change the approval result. IDM records an explicit
+escalated state and the target function; Policy authorizes only a current holder
+of that target for the escalated decision. Missing, malformed, vacant, expired,
+cyclic, over-depth, or tightened routes fail closed with their reason preserved
+in the decision and transition evidence.