fix: always autoplay after generation and resume TTS on HTMX chapter swap

scraper/internal/server/ui.go

@@ -2927,7 +2927,12 @@ const chapterTmpl = `
     highlightPara(0);
     generateAudio(CHAPTER_N, function (url) {
       if (stale()) return;
-      if (autoplay) audio.autoplay = true;
+      // Always set autoplay=true before load(): the browser needs this hint set
+      // synchronously before load() regardless of whether we got here via a user
+      // gesture or a programmatic trigger (e.g. chapter transition).  The canplay
+      // handler will call play() as well, but autoplay on the element is the only
+      // reliable path after an async fetch where the gesture stack is gone.
+      audio.autoplay = true;
       audio.src = url; audio.load();
       audio.playbackRate = getSpeed();
       registerMediaSession();
@@ -2943,7 +2948,15 @@ const chapterTmpl = `
     startAudio();
   };
 
-  window.__ttsBeforeSwap = function () { window.__ttsGen++; stop(); };
+  window.__ttsBeforeSwap = function () {
+    // If TTS is active (generating or has audio loaded), persist the autostart
+    // flag so the incoming chapter's init code will restart TTS automatically.
+    var wasActive = currentAudioCtrl !== null || (audio.src && !audio.ended);
+    if (wasActive) {
+      try { localStorage.setItem('tts_autostart', '1'); } catch(_) {}
+    }
+    window.__ttsGen++; stop();
+  };
   document.body.addEventListener('htmx:beforeSwap', window.__ttsBeforeSwap);
 
   var _autostart = false;