Fix: rename onPageStarted to onPageStart (correct GV API name), url non-null

app/src/main/java/dev/nova/browser/TabManager.kt

@@ -19,7 +19,8 @@ import java.io.File
  *
  * GeckoView does not expose canGoBack()/canGoForward() as polling methods —
  * navigation state arrives via NavigationDelegate callbacks, so we track it
- * here per tab. Loading state and progress arrive via ProgressDelegate.
+ * here per tab. Loading state and progress arrive via ProgressDelegate
+ * (onPageStart / onProgressChange / onPageStop, per the GV javadoc).
  *
  * M1 session restore: open-tab URLs + the active tab index are persisted to
  * a JSON file on every tab change and on activity stop, and reloaded on cold
@@ -106,8 +107,8 @@ class TabManager(private val runtime: GeckoRuntime, private val context: Context
             }
         }
         session.progressDelegate = object : GeckoSession.ProgressDelegate {
-            // GV 147 signature: url is nullable here.
-            override fun onPageStarted(session: GeckoSession, url: String?) {
+            // GV 147: onPageStart(session, url: String) — non-null url.
+            override fun onPageStart(session: GeckoSession, url: String) {
                 loadingStates[tabId] = true
                 progressStates[tabId] = 0
             }