feat(kanban): persist board, reference pages, and run agents

Replace the localStorage kanban with the backend-backed board, add typed clients
and a React hook with optimistic updates. Cards can reference static doc pages
and user-created custom pages (new "custom" reference type with purple chips).

Add the agentic orchestrator UI: a per-card panel to launch `pi` runs, watch a
live tool/thought stream over SSE, steer mid-run, and stop — while the board
stays fully interactive. The board page wires the orchestrator and custom-pages
stores into every card.

apps/docs/src/lib/orchestratorApi.ts

@@ -0,0 +1,102 @@
+/**
+ * Typed client for the @void-nav/api orchestrator backend.
+ *
+ * The orchestrator turns the implementation board into an agentic system: each
+ * run hands a kanban card to a `pi` subprocess (running inside an isolated git
+ * worktree) and streams its progress back to the UI. The agent drives the board
+ * and the documentation through the server's internal endpoints, so the board
+ * stays fully interactive and the docs remain the central store of truth.
+ *
+ * Keep these types in sync with `apps/api/src/types.ts`.
+ */
+
+export type RunStatus = 'queued' | 'running' | 'completed' | 'failed' | 'stopped';
+
+export interface AgentRun {
+  id: string;
+  cardId: string;
+  status: RunStatus;
+  useWorktree: boolean;
+  branch: string | null;
+  worktreePath: string | null;
+  prompt: string;
+  summary: string | null;
+  commitSha: string | null;
+  error: string | null;
+  createdAt: string;
+  startedAt: string | null;
+  finishedAt: string | null;
+}
+
+export type RunEventType =
+  | 'status'
+  | 'text'
+  | 'tool_start'
+  | 'tool_end'
+  | 'log'
+  | 'done'
+  | 'error';
+
+export interface RunEvent {
+  seq?: number;
+  type: RunEventType;
+  data: Record<string, unknown>;
+  createdAt?: string;
+}
+
+const BASE = '/api/orchestrator';
+
+class ApiError extends Error {
+  constructor(message: string, readonly status: number) {
+    super(message);
+    this.name = 'ApiError';
+  }
+}
+
+async function req<T>(path: string, init?: RequestInit): Promise<T> {
+  const res = await fetch(`${BASE}${path}`, {
+    ...init,
+    headers: { 'Content-Type': 'application/json', ...(init?.headers ?? {}) },
+  });
+  if (!res.ok) {
+    let detail = `${res.status} ${res.statusText}`;
+    try {
+      const body = await res.json();
+      if (body?.error) detail = body.error;
+    } catch {
+      /* keep status text */
+    }
+    throw new ApiError(detail, res.status);
+  }
+  if (res.status === 204) return undefined as T;
+  return (await res.json()) as T;
+}
+
+export interface StartRunInput {
+  cardId: string;
+  prompt?: string;
+  useWorktree?: boolean;
+  cleanupOnFinish?: boolean;
+}
+
+export const orchestratorApi = {
+  listRuns: (cardId?: string) =>
+    req<{ runs: AgentRun[] }>(`/runs${cardId ? `?cardId=${encodeURIComponent(cardId)}` : ''}`),
+
+  getRun: (id: string, since = 0) =>
+    req<{ run: AgentRun; events: RunEvent[] }>(`/runs/${id}?since=${since}`),
+
+  startRun: (input: StartRunInput) =>
+    req<{ run: AgentRun }>(`/runs`, { method: 'POST', body: JSON.stringify(input) }),
+
+  messageRun: (id: string, text: string, mode: 'steer' | 'followUp') =>
+    req<{ ok: boolean }>(`/runs/${id}/message`, {
+      method: 'POST',
+      body: JSON.stringify({ text, mode }),
+    }),
+
+  stopRun: (id: string) =>
+    req<{ ok: boolean }>(`/runs/${id}/stop`, { method: 'POST' }),
+
+  deleteRun: (id: string) => req<void>(`/runs/${id}`, { method: 'DELETE' }),
+};