refactor(ui/alerts): derive option lists + form-state types from schema.d.ts

Closes item 5 on the Plan 03 cleanup triage. The option arrays
("METRICS", "COMPARATORS", KIND_OPTIONS, SEVERITY_OPTIONS, FIRE_MODES)
scattered across RouteMetricForm / JvmMetricForm / ExchangeMatchForm /
ConditionStep / ScopeStep were hand-typed string literals. They drifted
silently — P95_LATENCY_MS appeared in a dropdown without a backend
counterpart (caught at runtime in bcde6678); JvmMetric.LATEST and
Comparator.EQ existed on the backend but were missing from the UI all
along.

Fix: new `ui/src/api/alerting-enums.ts` derives every enum from
schema.d.ts and pairs each with a `Record<T, string>` label map.
TypeScript enforces exhaustiveness — adding or removing a backend
value fails the build of this file until the label map is updated.
Every consumer imports the generated `*_OPTIONS` array.

Covered (schema-derived):
  - ConditionKind            → CONDITION_KIND_OPTIONS
  - Severity                 → SEVERITY_OPTIONS
  - RouteMetric              → ROUTE_METRIC_OPTIONS
  - Comparator               → COMPARATOR_OPTIONS (adds EQ that was missing)
  - JvmAggregation           → JVM_AGGREGATION_OPTIONS (adds LATEST that was missing)
  - ExchangeMatch.fireMode   → EXCHANGE_FIRE_MODE_OPTIONS
  - AlertRuleTarget.kind     → TARGET_KIND_OPTIONS

form-state.ts: `severity: 'CRITICAL' | 'WARNING' | 'INFO'` and
`kind: 'USER' | 'GROUP' | 'ROLE'` literal unions swapped for the
derived `Severity` / `TargetKind` aliases.

Not covered, backend types them as `String` (no `@Schema(allowableValues)`
annotation yet):
  - AgentStateCondition.state
  - DeploymentStateCondition.states
  - LogPatternCondition.level
  - ExchangeFilter.status
  - JvmMetricCondition.metric

These stay hand-typed with a pointer-comment. Follow-up: add
`@Schema(allowableValues = …)` to the Java record components so the
enums land in schema.d.ts; then fold them into alerting-enums.ts.

Plus: gitnexus index-stats refresh in AGENTS.md/CLAUDE.md from the
post-deploy reindex.

Verified: ui build green, 49/49 vitest pass.

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

ui/src/pages/Alerts/RuleEditor/form-state.ts

@@ -4,6 +4,7 @@ import type {
   ConditionKind,
   AlertCondition,
 } from '../../../api/queries/alertRules';
+import type { Severity, TargetKind } from '../../../api/alerting-enums';
 
 export type WizardStep = 'scope' | 'condition' | 'trigger' | 'notify' | 'review';
 export const WIZARD_STEPS: WizardStep[] = ['scope', 'condition', 'trigger', 'notify', 'review'];
@@ -11,7 +12,7 @@ export const WIZARD_STEPS: WizardStep[] = ['scope', 'condition', 'trigger', 'not
 export interface FormState {
   name: string;
   description: string;
-  severity: 'CRITICAL' | 'WARNING' | 'INFO';
+  severity: Severity;
   enabled: boolean;
 
   // Scope (radio: env-wide | app | route | agent)
@@ -36,7 +37,7 @@ export interface FormState {
     headerOverrides: Array<{ key: string; value: string }>;
   }>;
 
-  targets: Array<{ kind: 'USER' | 'GROUP' | 'ROLE'; targetId: string }>;
+  targets: Array<{ kind: TargetKind; targetId: string }>;
 }
 
 export function initialForm(existing?: AlertRuleResponse): FormState {
@@ -102,7 +103,7 @@ export function initialForm(existing?: AlertRuleResponse): FormState {
         .map(([key, value]) => ({ key, value })),
     })),
     targets: (existing.targets ?? []).map((t) => ({
-      kind: (t.kind ?? 'USER') as 'USER' | 'GROUP' | 'ROLE',
+      kind: (t.kind ?? 'USER') as TargetKind,
       targetId: t.targetId ?? '',
     })),
   };