feat(quick-260329-ton): replace textContent with innerHTML + renderInlineMarkdown at all AI-text insertion points

- src/app.ts: greeting text now renders inline markdown
- src/ui/screens.ts: letter intro text now renders inline markdown
- src/forest/reward.ts: forest comment now renders inline markdown
- All 3 sites use innerHTML with XSS-safe renderInlineMarkdown

src/app.ts

@@ -1,6 +1,7 @@
 import { speakText } from "./audio/speech";
 import { companions } from "./companion/characters";
 import { getGreeting } from "./companion/companion";
+import { renderInlineMarkdown } from "./utils/markdown";
 import { initRewardScreen, startPreGeneration } from "./forest/reward";
 import { initForestScreen, renderForestScene } from "./forest/scene";
 import { getProgress, openDB, saveProgress } from "./storage/db";
@@ -224,7 +225,7 @@ 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;
+				textEl.innerHTML = renderInlineMarkdown(text);
 				speakText(text);
 			});
 		}