refactor(admin): drop simulations/experiments/models pages; group nav into sections

Removes the in-shell MLOps pages (experiments, models, simulations) and their
client API helpers in favour of external MLflow/Airflow links. Nav is regrouped
into Signals / Recommender status / Ops sections for clarity.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

apps/admin/src/lib/api.ts

@@ -220,67 +220,3 @@ export function saveQuery(name: string, querySql: string) {
 export function deleteSavedQuery(id: string) {
   return apiFetch<{ ok: boolean }>(`/admin/saved-queries/${id}`, { method: 'DELETE' });
 }
-
-// ── Simulation ─────────────────────────────────────────────────────────────
-
-export interface PolicySummary {
-  total_reward: number;
-  mean_reward: number;
-  n_pulls: number;
-  cumulative_rewards: number[];
-  action_counts: Record<string, number>;
-}
-
-export interface SimRun {
-  id: string;
-  policyA: string;
-  policyB: string;
-  nUsers: number;
-  nRounds: number;
-  tasksPerRound: number;
-  useLlm: boolean;
-  status: 'pending' | 'running' | 'done' | 'failed';
-  summaryJson: string | null;
-  winner: string | null;
-  personaBreakdownJson: string | null;
-  createdAt: string;
-  finishedAt: string | null;
-  isRunning?: boolean;
-}
-
-export interface SimEvent {
-  id: string;
-  runId: string;
-  round: number;
-  userId: string;
-  persona: string;
-  policy: string;
-  tipContent: string;
-  priority: number;
-  isOverdue: boolean;
-  action: string;
-  rewardMilli: number;
-  hour: number;
-  dayOfWeek: number;
-}
-
-export function startSimulation(params: {
-  nUsers: number;
-  nRounds: number;
-  tasksPerRound: number;
-  useLlm: boolean;
-  policies: string[];
-}) {
-  return apiFetch<{ id: string; status: string }>('/admin/simulate/start', {
-    method: 'POST',
-    body: JSON.stringify(params),
-  });
-}
-
-export function getSimRuns() {
-  return apiFetch<{ runs: SimRun[] }>('/admin/simulate/runs');
-}
-
-export function getSimRun(id: string) {
-  return apiFetch<{ run: SimRun; events: SimEvent[] }>(`/admin/simulate/${id}`);
-}