fix: playlist panel UX issues

- Phantom playlists: stop pushing locally on create; let PLAYLIST_CREATED
  STOMP event add the entry to avoid the REST/STOMP race that doubled items
- Row click: attach toggle-expand listener on the li instead of the name
  span only; add cursor:pointer to .playlist-list-item
- Input styling: apply surface-3 bg, border, radius, and color to
  .playlist-create-row input and .playlist-rename-form input with focus ring
- Play/pause error toast: apiFetch now skips json() when response has no
  application/json Content-Type (empty 200 body from play/pause endpoints)

src/main/resources/static/css/styles.css

@@ -1069,6 +1069,14 @@ button:disabled:hover {
     font-size: 12px;
     padding: 5px 8px;
     min-width: 0;
+    background: var(--color-surface-3);
+    border: 1px solid var(--color-border);
+    border-radius: 6px;
+    color: var(--color-text);
+    outline: none;
+}
+.playlist-create-row input:focus {
+    border-color: var(--color-accent-border);
 }
 
 .playlist-list {
@@ -1095,6 +1103,7 @@ button:disabled:hover {
     border-radius: 8px;
     border: 1px solid transparent;
     transition: background 0.12s;
+    cursor: pointer;
 }
 
 .playlist-list-item:hover {
@@ -1171,6 +1180,14 @@ button:disabled:hover {
     font-size: 12px;
     padding: 4px 7px;
     min-width: 0;
+    background: var(--color-surface-3);
+    border: 1px solid var(--color-border);
+    border-radius: 6px;
+    color: var(--color-text);
+    outline: none;
+}
+.playlist-rename-form input:focus {
+    border-color: var(--color-accent-border);
 }
 
 /* Playback controls */

src/main/resources/static/js/playlist.js

@@ -62,7 +62,8 @@
         if (csrfToken && csrfHeader) headers[csrfHeader] = csrfToken;
         const response = await fetch(`${apiBase()}${path}`, { ...options, headers });
         if (!response.ok) throw new Error(`Request failed: ${response.status}`);
-        if (response.status === 204) return null;
+        const ct = response.headers.get("content-type") || "";
+        if (response.status === 204 || !ct.includes("application/json")) return null;
         return response.json();
     }
 
@@ -160,10 +161,10 @@
         if (!name) { showToast("Enter a playlist name.", "info"); return; }
         try {
             const view = await apiFetch("", { method: "POST", body: JSON.stringify({ name }) });
-            playlists.push(view);
             input.value = "";
-            renderPlaylistList();
+            // Don't push locally — the PLAYLIST_CREATED STOMP event will add it.
-            expandPlaylist(view.id);
+            // Just pre-set the expanded id so it opens as soon as the event renders it.
+            if (view?.id) expandedPlaylistId = view.id;
         } catch {
             showToast("Could not create playlist.", "error");
         }
@@ -186,11 +187,11 @@
             const li = document.createElement("li");
             li.className = "playlist-list-item" + (p.id === expandedPlaylistId ? " expanded" : "") + (p.id === activePlaylistId ? " active" : "");
             li.dataset.id = p.id;
+            li.addEventListener("click", () => toggleExpand(p.id));
 
             const nameSpan = document.createElement("span");
             nameSpan.className = "playlist-list-name";
             nameSpan.textContent = p.name;
-            nameSpan.addEventListener("click", () => toggleExpand(p.id));
 
             const actions = document.createElement("div");
             actions.className = "playlist-list-actions";