feat: HLS streaming, transcripts, agent course generation & landing-page course previews (#663)

New features:
- HLS video encoding/streaming (hls routes, hls-encoder) and a media
  transcripts pipeline (transcripts route + media-transcript queries)
- AI assistant chat vs. run model: agent-course-generation worker/queue,
  run-monitor pane, chat-changes card, content ask-ai bar
- Per-theme course-page previews across org landing-page themes (bold,
  classic, corporate, editorial, etc.) with a shared course token/component set
- View-as-student mode and login-link / link-invite invite flows

Refactor:
- Extract packages/core consolidating config (env, storage, dashboard-url),
  services and utils previously duplicated under apps/api/src/config
- Remove legacy agent service modules (chat-tools, chat-context,
  context-window, document, fetch-url, lesson-content)
- Relax Cross-Origin-Resource-Policy to allow cross-origin media embedding
- Add format script to tenant-router so turbo run format covers it

packages/utils/src/errors/index.ts

@@ -0,0 +1,29 @@
+import { ErrorCodes, type ErrorCode } from '../constants';
+
+export { ErrorCodes, type ErrorCode };
+
+/**
+ * Standard HTTP status code value. Kept as a structural `number` so this
+ * module stays free of HTTP-framework deps (hono). The api layer narrows
+ * this when handing the value to its response helpers.
+ */
+export type AppErrorStatusCode = number;
+
+/**
+ * Standard application error with code for easy identification.
+ *
+ * Lives in `@cio/utils/errors` so it can be thrown from any workspace package
+ * (notably `@cio/core`) without those packages depending on `@cio/api`.
+ * HTTP-shaped helpers like `handleError` stay in `@cio/api`.
+ */
+export class AppError extends Error {
+  constructor(
+    error: string | Error,
+    public code: string,
+    public statusCode: AppErrorStatusCode = 500,
+    public field?: string
+  ) {
+    super(error instanceof Error ? error.message : error);
+    this.name = 'AppError';
+  }
+}