Refine travel reimbursement steward flow

Align planner, runtime rules, and policy assets so travel guidance
matches the updated reimbursement workflow.

web/src/composables/useAppShell.js

@@ -9,6 +9,7 @@ import { fetchAllApprovalExpenseClaims, fetchExpenseClaimDetail } from '../servi
 import { fetchOntologyParse } from '../services/ontology.js'
 import { fetchLatestConversation } from '../services/orchestrator.js'
 import { clearAssistantSessionSnapshotForDraftClaim } from '../utils/assistantSessionSnapshot.js'
+import { ASSISTANT_SCOPE_SESSION_STEWARD } from '../utils/assistantSessionScope.js'
 import { buildDetailAlerts } from '../utils/detailAlerts.js'
 import { normalizeRequestForUi } from '../utils/requestViewModel.js'
 import {
@@ -371,6 +372,9 @@ export function useAppShell() {
     if (!prompt) {
       return fallbackSessionType
     }
+    if (fallbackSessionType === ASSISTANT_SCOPE_SESSION_STEWARD) {
+      return fallbackSessionType
+    }
 
     try {
       const ontology = await fetchOntologyParse(