feat(client): add UI kit, data layer, app shell, and Table component

- design token system (Atlantis, Kimberly, Powder Ash palette)
- Button, Badge, Input, Select, Card, SidePanel, Breadcrumbs components
- generic typed Table<T> component with loading/empty states
- API data layer: typed fetch client for environments, keys, sessions, scenarios
- Vite dev proxy targeting server on port 13000
- App shell with SidePanel nav and four entity pages (Environments, Keys, Sessions, Scenarios)
- Storybook config with dark/light theme toggle and a11y addon

client/src/api/client.ts

@@ -0,0 +1,109 @@
+import type {
+  PaginatedResponse,
+  Environment,
+  KeysResponse,
+  Session,
+  Scenario,
+  ScenarioRun,
+  ScenarioStep,
+} from './types';
+
+// In dev, Vite proxies /environments /sessions /scenarios /keys to localhost:3000.
+// In production (or when VITE_API_URL is set) we hit the configured origin directly.
+const BASE_URL: string = (import.meta.env.VITE_API_URL as string | undefined) ?? '';
+
+async function request<T>(path: string, init?: RequestInit): Promise<T> {
+  const res = await fetch(`${BASE_URL}${path}`, {
+    headers: { 'Content-Type': 'application/json', ...init?.headers },
+    ...init,
+  });
+  if (!res.ok) {
+    const text = await res.text().catch(() => res.statusText);
+    throw new Error(`${res.status} ${text}`);
+  }
+  if (res.status === 204) return undefined as T;
+  return res.json() as Promise<T>;
+}
+
+// ── Environments ──────────────────────────────────────────────────────────────
+
+export const environments = {
+  list(page = 1, limit = 50): Promise<PaginatedResponse<Environment>> {
+    return request(`/environments?page=${page}&limit=${limit}`);
+  },
+  get(id: number): Promise<Environment> {
+    return request(`/environments/${id}`);
+  },
+  create(name: string, urls: Environment['urls']): Promise<Environment> {
+    return request('/environments', {
+      method: 'POST',
+      body: JSON.stringify({ name, urls }),
+    });
+  },
+  update(id: number, patch: Partial<Pick<Environment, 'name' | 'urls'>>): Promise<Environment> {
+    return request(`/environments/${id}`, {
+      method: 'PATCH',
+      body: JSON.stringify(patch),
+    });
+  },
+  remove(id: number): Promise<void> {
+    return request(`/environments/${id}`, { method: 'DELETE' });
+  },
+};
+
+// ── Keys ──────────────────────────────────────────────────────────────────────
+
+export const keys = {
+  list(): Promise<KeysResponse> {
+    return request('/keys');
+  },
+};
+
+// ── Sessions ──────────────────────────────────────────────────────────────────
+
+export const sessions = {
+  list(page = 1, limit = 50): Promise<PaginatedResponse<Session>> {
+    return request(`/sessions?page=${page}&limit=${limit}`);
+  },
+  remove(id: number): Promise<void> {
+    return request(`/sessions/${id}`, { method: 'DELETE' });
+  },
+};
+
+// ── Scenarios ─────────────────────────────────────────────────────────────────
+
+export const scenarios = {
+  list(page = 1, limit = 50): Promise<PaginatedResponse<Scenario>> {
+    return request(`/scenarios?page=${page}&limit=${limit}`);
+  },
+  get(id: number): Promise<Scenario & { steps: ScenarioStep[] }> {
+    return request(`/scenarios/${id}`);
+  },
+  create(name: string): Promise<Scenario> {
+    return request('/scenarios', {
+      method: 'POST',
+      body: JSON.stringify({ name }),
+    });
+  },
+  update(id: number, patch: Partial<Pick<Scenario, 'name'>>): Promise<Scenario> {
+    return request(`/scenarios/${id}`, {
+      method: 'PATCH',
+      body: JSON.stringify(patch),
+    });
+  },
+  remove(id: number): Promise<void> {
+    return request(`/scenarios/${id}`, { method: 'DELETE' });
+  },
+  run(id: number): Promise<ScenarioRun> {
+    return request(`/scenarios/${id}/run`, { method: 'POST' });
+  },
+  getRun(scenarioId: number, runId: number): Promise<ScenarioRun> {
+    return request(`/scenarios/${scenarioId}/run/${runId}`);
+  },
+  waitForRun(scenarioId: number, runId: number): Promise<ScenarioRun> {
+    return request(`/scenarios/${scenarioId}/run/${runId}/wait`, { method: 'POST' });
+  },
+  listRuns(scenarioId: number, page = 1, limit = 20): Promise<PaginatedResponse<ScenarioRun>> {
+    return request(`/scenarios/${scenarioId}/runs?page=${page}&limit=${limit}`);
+  },
+};