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/ui/src/custom/public-course/exercise-view.svelte

@@ -15,7 +15,11 @@
   import Callout from './callout.svelte';
   import type { PublicCourseCalloutAnimation, PublicCourseCalloutData, PublicExerciseViewData } from './types';
   import type { PublicExerciseStoredAttempt } from './public-exercise-attempts-storage';
-  import { readPublicExerciseAttempts, writePublicExerciseAttempts } from './public-exercise-attempts-storage';
+  import {
+    cloneAnswersByKey,
+    readPublicExerciseAttempts,
+    writePublicExerciseAttempts
+  } from './public-exercise-attempts-storage';
 
   interface Props {
     exercise: PublicExerciseViewData;
@@ -77,7 +81,7 @@
       const defaultIndex = rows.length - 1;
       selectValue = String(defaultIndex);
       const row = rows[defaultIndex];
-      answers = structuredClone(row.answersByKey);
+      answers = cloneAnswersByKey(row.answersByKey);
       submitted = true;
     });
   });
@@ -95,7 +99,7 @@
 
     selectValue = selected;
     submitted = true;
-    answers = structuredClone(persistedAttempts[idx].answersByKey);
+    answers = cloneAnswersByKey(persistedAttempts[idx].answersByKey);
   }
 
   function handleAnswerChange(question: ExerciseQuestionModel, answer: AnswerData | null) {
@@ -317,7 +321,7 @@
 
     const snapshot: PublicExerciseStoredAttempt = {
       savedAt: new Date().toISOString(),
-      answersByKey: structuredClone(answers),
+      answersByKey: cloneAnswersByKey(answers),
       correctCount: correct,
       totalGradable: tot
     };