refine: align positive update presentation

Display the primary release heading as What's new?, render the install and active download states in the success palette, and reserve red exclusively for cancellation and failure.

renderer/app.js

@@ -7467,9 +7467,12 @@ function _renderUpdateReleaseNotes(container, value) {
         : 'update-release-line';
     const source = heading ? heading[2] : bullet ? `• ${bullet[1]}` : line;
     const cleaned = _cleanUpdateReleaseText(source);
+    const displayText = className === 'update-release-heading' && cleaned.toLocaleLowerCase('en-US') === "what's new"
+      ? `${cleaned}?`
+      : cleaned;
     const available = 2400 - consumed;
     if (available <= 0) break;
-    const text = cleaned.length > available ? `${cleaned.slice(0, Math.max(0, available - 1))}…` : cleaned;
+    const text = displayText.length > available ? `${displayText.slice(0, Math.max(0, available - 1))}…` : displayText;
     const element = document.createElement('div');
     element.className = className;
     element.textContent = text;

renderer/index.html

@@ -174,7 +174,7 @@
       </div>
       <div class="update-dialog-actions">
         <button class="btn btn-secondary" id="dismissUpdateBtn">Abbrechen</button>
-        <button class="btn btn-primary" id="installUpdateBtn">Jetzt installieren</button>
+        <button class="btn btn-success" id="installUpdateBtn">Jetzt installieren</button>
       </div>
     </section>
   </div>

renderer/styles.css

@@ -2540,6 +2540,12 @@ select.hs-input { max-width: none; width: auto; min-width: 140px; }
   transition: width .48s cubic-bezier(.22, 1, .36, 1), background-color .16s ease;
 }
 
+.update-progress-track span[data-state="downloading"],
+.update-progress-track span[data-state="verifying"],
+.update-progress-track span[data-state="prepared"] {
+  background: var(--success);
+}
+
 .update-progress-track span[data-state="aborted"],
 .update-progress-track span[data-state="error"] {
   background: var(--danger);