feat(simulate): MLflow tracking, Airflow DAG integration, health checks for mlflow/airflow

- sim_runs schema: add judge_mode, n_policies, airflow_dag_run_id, mlflow_run_id columns
- admin health endpoint: add mlflow + airflow checks (Basic auth for Airflow API)
- admin nav: add Simulations page link; rename section label
- runner.py: optional MLflow experiment tracking; multi-policy support
- sim_dag.py: Airflow DAG for offline sim pipeline
- admin simulate page + API client methods for sim runs
- shared-types tsconfig: exclude test files from build

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/admin/src/lib/api.ts

@@ -262,3 +262,49 @@ export function saveQuery(name: string, querySql: string) {
 export function deleteSavedQuery(id: string) {
   return apiFetch<{ ok: boolean }>(`/admin/saved-queries/${id}`, { method: 'DELETE' });
 }
+
+// ── Simulations ────────────────────────────────────────────────────────────
+
+export interface SimRun {
+  id: string;
+  policyA: string;
+  policyB: string;
+  nUsers: number;
+  nRounds: number;
+  tasksPerRound: number;
+  judgeMode: string;
+  nPolicies: number;
+  status: 'pending' | 'running' | 'done' | 'failed';
+  summaryJson: string | null;
+  winner: string | null;
+  personaBreakdownJson: string | null;
+  airflowDagRunId: string | null;
+  mlflowRunId: string | null;
+  createdAt: string;
+  finishedAt: string | null;
+}
+
+export interface SimStartRequest {
+  nUsers?: number;
+  nRounds?: number;
+  tasksPerRound?: number;
+  judgeMode?: 'rule' | 'llm';
+  policies?: string[];
+}
+
+export function startSimulation(req: SimStartRequest) {
+  return apiFetch<{ id: string; status: string; airflow_dag_run_id?: string }>(
+    '/admin/simulate/start',
+    { method: 'POST', body: JSON.stringify(req) },
+  );
+}
+
+export function getSimulationRuns() {
+  return apiFetch<{ runs: SimRun[] }>('/admin/simulate/runs');
+}
+
+export function getSimulationRun(id: string) {
+  return apiFetch<{ run: SimRun & { isRunning: boolean }; events: unknown[] }>(
+    `/admin/simulate/${id}`,
+  );
+}