feat(04-04): wire audio and speech into lesson, reward, forest, and app

- playCorrectSound() on correct keypress in letter and word exercises
- playRewardSound() when reward image appears
- speakText() for companion comment on reward screen
- playForestElementSound() when new forest element renders
- speakText() for companion greeting on forest screen

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/app.ts

@@ -1,11 +1,12 @@
-import type { ScreenName } from "./types";
-import { openDB, getProgress, saveProgress } from "./storage/db";
-import { initWelcomeScreen, initLessonScreen } from "./ui/screens";
-import { initForestScreen, renderForestScene } from "./forest/scene";
-import { startPreGeneration, initRewardScreen } from "./forest/reward";
-import { getGreeting } from "./companion/companion";
+import { speakText } from "./audio/speech";
 import { companions } from "./companion/characters";
-import { showParentCodePrompt, initParentScreen } from "./ui/parent";
+import { getGreeting } from "./companion/companion";
+import { initRewardScreen, startPreGeneration } from "./forest/reward";
+import { initForestScreen, renderForestScene } from "./forest/scene";
+import { getProgress, openDB, saveProgress } from "./storage/db";
+import type { ScreenName } from "./types";
+import { initParentScreen, showParentCodePrompt } from "./ui/parent";
+import { initLessonScreen, initWelcomeScreen } from "./ui/screens";
 
 let db: IDBDatabase;
 let lessonCleanup: (() => void) | null = null;
@@ -215,6 +216,7 @@ export async function initApp(): Promise<void> {
 			// Fetch greeting async (shows immediately with avatar, text fills in)
 			getGreeting(progress.selectedCharacter, db).then((text) => {
 				textEl.textContent = text;
+				speakText(text);
 			});
 		}
 	} else {