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

PRD-TRACKER.md

@@ -13,12 +13,14 @@ Use this file to keep a single prioritized view of all PRDs.
 | 5 | 3 | `prd/course-cohorts` | todo |
 | 6 | 7 | `prd/email-template-customization` | todo |
 | 7 | - | `prd/selective-exercise-assignment` | todo |
+| - | - | `prd/scorm-support` | todo |
 | - | 4 | `prd/course-content-search` | todo |
 | - | 9 | `prd/onboarding-ai-bootstrap` | todo |
 | - | 10 | `prd/pricing-improvements` | todo |
 | - | 12 | `prd/public-courses` | todo |
 | - | - | `prd/customer-course-documentation` | todo |
 | - | - | `prd/walkthrough-widget` | draft |
+| - | - | `prd/copy-page-as-markdown` | todo |
 | - | 15 | `prd/webhooks` | todo |
 
 ## DONE (Completed PRDs)