fix: register MediaSession action handlers for iOS lock screen resume

Without explicit setActionHandler('play'/'pause'/...) the browser uses
default handling which on iOS Safari stops working after ~1 min of
pause in background/locked state (AudioSession gets suspended and the
lock screen button can't resume it without a direct user gesture).

Registering handlers in the layout (where audioEl lives) ensures:
- play/pause call audioEl directly — iOS treats this as a trusted
  gesture and allows .play() even from the lock screen
- seekbackward/seekforward map to ±15s / ±30s
- playbackState stays in sync so the lock screen shows the right icon

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/internal/backend/handlers_textgen.go

@@ -99,12 +99,17 @@ func (s *Server) handleAdminTextGenChapterNames(w http.ResponseWriter, r *http.R
 	}
 
 	systemPrompt := `You are a chapter title editor for a web novel platform. ` +
-		`The user will provide a list of chapter numbers with their current titles, ` +
-		`and a naming pattern. Your task is to produce a renamed version of every chapter ` +
-		`following the pattern exactly. ` +
-		`Respond ONLY with a JSON array — no prose, no markdown fences, no explanation. ` +
-		`Each element must be an object: {"number": <int>, "title": <string>}. ` +
-		`Output every chapter in the input list. Do not skip any.`
+		`The user provides a list of chapter numbers with their current titles, ` +
+		`and a naming pattern template. ` +
+		`Your job: produce one new title for every chapter, following the pattern exactly. ` +
+		`Pattern placeholders: {n} = the chapter number (integer), {scene} = a very short (2–5 word) scene hint derived from the existing title. ` +
+		`RULES: ` +
+		`1. Do NOT include the chapter number inside the title text — the {n} placeholder is already in the pattern. ` +
+		`2. Do NOT include any prefix like "Chapter X -" or "Chapter X:" inside the title field itself. ` +
+		`3. The "title" field in your JSON must be the fully-rendered string (e.g. if pattern is "Chapter {n}: {scene}", output "Chapter 3: The Bet"). ` +
+		`4. Respond ONLY with a raw JSON array — no prose, no markdown fences, no explanation. ` +
+		`5. Each element: {"number": <int>, "title": <string>}. ` +
+		`6. Output every chapter in the input list, in order. Do not skip any.`
 
 	userPrompt := fmt.Sprintf(
 		"Naming pattern: %s\n\nChapters:\n%s",
@@ -117,8 +122,14 @@ func (s *Server) handleAdminTextGenChapterNames(w http.ResponseWriter, r *http.R
 		model = cfai.DefaultTextModel
 	}
 
+	// Default to 4096 tokens so large chapter lists are not truncated.
+	maxTokens := req.MaxTokens
+	if maxTokens <= 0 {
+		maxTokens = 4096
+	}
+
 	s.deps.Log.Info("admin: text-gen chapter-names requested",
-		"slug", req.Slug, "chapters", len(chapters), "model", model)
+		"slug", req.Slug, "chapters", len(chapters), "model", model, "max_tokens", maxTokens)
 
 	raw, genErr := s.deps.TextGen.Generate(r.Context(), cfai.TextRequest{
 		Model: model,
@@ -126,7 +137,7 @@ func (s *Server) handleAdminTextGenChapterNames(w http.ResponseWriter, r *http.R
 			{Role: "system", Content: systemPrompt},
 			{Role: "user", Content: userPrompt},
 		},
-		MaxTokens: req.MaxTokens,
+		MaxTokens: maxTokens,
 	})
 	if genErr != nil {
 		s.deps.Log.Error("admin: text-gen chapter-names failed", "err", genErr)

ui/src/routes/+layout.svelte

@@ -192,6 +192,50 @@
 		return () => clearTimeout(id);
 	});
 
+	// ── MediaSession action handlers ────────────────────────────────────────────
+	// Without explicit handlers, iOS Safari loses lock-screen resume ability after
+	// ~1 minute of pause because it falls back to its own default which doesn't
+	// satisfy the user-gesture requirement for <audio>.play().
+	// Handlers registered here call audioEl directly so iOS trusts the gesture.
+	$effect(() => {
+		if (typeof navigator === 'undefined' || !('mediaSession' in navigator) || !audioEl) return;
+		const el = audioEl; // capture for closure
+
+		navigator.mediaSession.setActionHandler('play', () => {
+			el.play().catch(() => {});
+		});
+		navigator.mediaSession.setActionHandler('pause', () => {
+			el.pause();
+		});
+		navigator.mediaSession.setActionHandler('seekbackward', (d) => {
+			el.currentTime = Math.max(0, el.currentTime - (d.seekOffset ?? 15));
+		});
+		navigator.mediaSession.setActionHandler('seekforward', (d) => {
+			el.currentTime = Math.min(el.duration || 0, el.currentTime + (d.seekOffset ?? 30));
+		});
+		// previoustrack / nexttrack fall back to skip ±30s if no chapter nav available
+		try {
+			navigator.mediaSession.setActionHandler('previoustrack', () => {
+				el.currentTime = Math.max(0, el.currentTime - 30);
+			});
+			navigator.mediaSession.setActionHandler('nexttrack', () => {
+				el.currentTime = Math.min(el.duration || 0, el.currentTime + 30);
+			});
+		} catch { /* some browsers don't support these */ }
+
+		return () => {
+			(['play', 'pause', 'seekbackward', 'seekforward'] as MediaSessionAction[]).forEach((a) => {
+				try { navigator.mediaSession.setActionHandler(a, null); } catch { /* ignore */ }
+			});
+		};
+	});
+
+	// Keep playbackState in sync so iOS lock screen shows the right button state
+	$effect(() => {
+		if (typeof navigator === 'undefined' || !('mediaSession' in navigator)) return;
+		navigator.mediaSession.playbackState = audioStore.isPlaying ? 'playing' : 'paused';
+	});
+
 	// ── Save audio time on pause/end (debounced 2s) ─────────────────────────
 	let audioTimeSaveTimer = 0;
 	function saveAudioTime() {

ui/src/routes/admin/text-gen/+page.svelte

@@ -71,6 +71,11 @@
 			);
 			chRawResponse = body.raw_response ?? '';
 			chUsedModel = body.model ?? '';
+			// If backend returned chapters:[] but we have a raw response, the model
+			// output was unparseable (likely truncated). Treat it as an error.
+			if (chProposals.length === 0 && chRawResponse.trim().length > 0) {
+				chError = 'Model response could not be parsed (output may be truncated). Raw response shown below.';
+			}
 		} catch {
 			chError = 'Network error.';
 		} finally {
@@ -287,6 +292,9 @@
 
 				{#if chError}
 					<p class="text-sm text-(--color-danger) bg-(--color-danger)/10 rounded-lg px-3 py-2">{chError}</p>
+					{#if chRawResponse}
+						<pre class="text-xs bg-(--color-surface-2) border border-(--color-border) rounded-lg p-3 overflow-auto max-h-48 text-(--color-muted) whitespace-pre-wrap break-words">{chRawResponse}</pre>
+					{/if}
 				{/if}
 			</div>