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/db/src/queries/agent/run-state.ts

@@ -253,6 +253,21 @@ export async function upsertAgentRunStep(input: UpsertAgentRunStepInput): Promis
   }
 }
 
+export async function getAgentRunStep(runId: string, stepKey: string): Promise<TAiAgentRunStep | null> {
+  try {
+    const [row] = await db
+      .select()
+      .from(schema.aiAgentRunStep)
+      .where(and(eq(schema.aiAgentRunStep.runId, runId), eq(schema.aiAgentRunStep.stepKey, stepKey)))
+      .limit(1);
+
+    return row ?? null;
+  } catch (error) {
+    console.error('getAgentRunStep error:', error);
+    throw new Error('Failed to get agent run step');
+  }
+}
+
 export async function listAgentRunSteps(runId: string): Promise<TAiAgentRunStep[]> {
   try {
     return await db