fix(ui): use describeApiError across remaining error-surface sites

Extends the previous describeApiError rollout to the rest of the UI.
Two symptom classes covered:

 - Bare e.message / err.message in toast descriptions would render
   "undefined" on Spring error bodies (plain objects without a proper
   Error prototype). Affected: OidcConfigPage (save/test/delete),
   ClaimMappingRulesModal (save + test), AgentHealth (dismiss),
   RouteControlBar (route action + replay).

 - Inline {String(error)} on load-failure banners would render
   "[object Object]". Affected: InboxPage, RulesListPage, SilencesPage,
   OutboundConnectionsPage.

Not touched: auth-store, AppsTab, UsersTab — they already guard with
`e instanceof Error` and fall back to a static string; replacing the
fallback with describeApiError would be a behavioral change best
evaluated separately.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ui/src/pages/Admin/ClaimMappingRulesModal.tsx

@@ -10,6 +10,7 @@ import {
 } from '../../api/queries/admin/claim-mappings';
 import type { ClaimMappingRule, TestResponse } from '../../api/queries/admin/claim-mappings';
 import { useRoles, useGroups } from '../../api/queries/admin/rbac';
+import { describeApiError } from '../../api/errors';
 import styles from './ClaimMappingRulesModal.module.css';
 
 const MATCH_OPTIONS = [
@@ -231,8 +232,8 @@ export default function ClaimMappingRulesModal({ open, onClose }: Props) {
 
       toast({ title: 'Rules saved', variant: 'success' });
       handleClose();
-    } catch (e: any) {
-      toast({ title: 'Failed to save rules', description: e.message, variant: 'error', duration: 86_400_000 });
+    } catch (e) {
+      toast({ title: 'Failed to save rules', description: describeApiError(e), variant: 'error', duration: 86_400_000 });
     } finally {
       setApplying(false);
     }
@@ -256,7 +257,7 @@ export default function ClaimMappingRulesModal({ open, onClose }: Props) {
     }));
     testRules.mutate({ rules, claims }, {
       onSuccess: (result) => setTestResult(result),
-      onError: (e) => setTestError(e.message),
+      onError: (e) => setTestError(describeApiError(e)),
     });
   }
 

ui/src/pages/Admin/OidcConfigPage.tsx

@@ -8,6 +8,7 @@ import { PageLoader } from '../../components/PageLoader';
 import { adminFetch } from '../../api/queries/admin/admin-api';
 import ClaimMappingRulesModal from './ClaimMappingRulesModal';
 import { useClaimMappingRules } from '../../api/queries/admin/claim-mappings';
+import { describeApiError } from '../../api/errors';
 import styles from './OidcConfigPage.module.css';
 import sectionStyles from '../../styles/section-card.module.css';
 
@@ -114,8 +115,8 @@ export default function OidcConfigPage() {
       setFormDraft(null);
       setEditing(false);
       toast({ title: 'Settings saved', description: 'OIDC configuration updated successfully.', variant: 'success' });
-    } catch (e: any) {
-      toast({ title: 'Failed to save OIDC configuration', description: e.message, variant: 'error', duration: 86_400_000 });
+    } catch (e) {
+      toast({ title: 'Failed to save OIDC configuration', description: describeApiError(e), variant: 'error', duration: 86_400_000 });
     } finally {
       setSaving(false);
     }
@@ -127,8 +128,8 @@ export default function OidcConfigPage() {
     try {
       const result = await adminFetch<{ status: string; authorizationEndpoint?: string }>('/oidc/test', { method: 'POST' });
       toast({ title: 'Connection test', description: `OIDC provider responded: ${result.status}`, variant: 'success' });
-    } catch (e: any) {
-      toast({ title: 'Connection test failed', description: e.message, variant: 'error', duration: 86_400_000 });
+    } catch (e) {
+      toast({ title: 'Connection test failed', description: describeApiError(e), variant: 'error', duration: 86_400_000 });
     } finally {
       setTesting(false);
     }
@@ -142,8 +143,8 @@ export default function OidcConfigPage() {
       setFormDraft(null);
       setEditing(false);
       toast({ title: 'Configuration deleted', description: 'OIDC configuration has been removed.', variant: 'warning' });
-    } catch (e: any) {
-      toast({ title: 'Failed to delete OIDC configuration', description: e.message, variant: 'error', duration: 86_400_000 });
+    } catch (e) {
+      toast({ title: 'Failed to delete OIDC configuration', description: describeApiError(e), variant: 'error', duration: 86_400_000 });
     }
   }
 

ui/src/pages/Admin/OutboundConnectionsPage.tsx

@@ -16,7 +16,7 @@ export default function OutboundConnectionsPage() {
   const { toast } = useToast();
 
   if (isLoading) return <PageLoader />;
-  if (error) return <div>Failed to load outbound connections: {String(error)}</div>;
+  if (error) return <div>Failed to load outbound connections: {describeApiError(error)}</div>;
 
   const rows = data ?? [];