chore: temporary diagnostics for embedded browser scrolling

Adds two temporary logs to pin down why the embedded browser doesn't scroll:
- provider side (NappletBrowserService): logs each MotionEvent that reaches the
  remote WebView, so we can see if touch crosses the SurfaceControlViewHost
  boundary at all (returns false, never consumes).
- client side (EmbeddedBrowserController): logs the SandboxedSdkView session
  state transitions (Idle/Loading/Active/Error).

To be reverted once the cause is confirmed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MgMpRcWj6y82LxLiwcuzmN

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/browser/EmbeddedBrowserController.kt

@@ -31,8 +31,11 @@ import android.os.IBinder
 import android.os.Looper
 import android.os.Message
 import android.os.Messenger
+import android.util.Log
 import androidx.annotation.RequiresApi
 import androidx.privacysandbox.ui.client.SandboxedUiAdapterFactory
+import androidx.privacysandbox.ui.client.view.SandboxedSdkUiSessionState
+import androidx.privacysandbox.ui.client.view.SandboxedSdkUiSessionStateChangedListener
 import androidx.privacysandbox.ui.client.view.SandboxedSdkView
 import androidx.privacysandbox.ui.core.SandboxedUiAdapter
 import com.vitorpamplona.amethyst.napplethost.NappletBrowserContract
@@ -98,6 +101,14 @@ class EmbeddedBrowserController(
         // Paint the surface placeholder in the app's theme background so there's no white flash before
         // the remote WebView delivers its first frame.
         view.setBackgroundColor(backgroundColor)
+        // DIAGNOSTIC (scrolling): log the surface session lifecycle so we can see if it reaches Active.
+        view.addStateChangedListener(
+            object : SandboxedSdkUiSessionStateChangedListener {
+                override fun onStateChanged(state: SandboxedSdkUiSessionState) {
+                    Log.w("BrowserSurfaceDiag", "DIAG session state: $state")
+                }
+            },
+        )
         pendingAdapter?.let {
             view.setAdapter(it)
             pendingAdapter = null

nappletHost/src/main/kotlin/com/vitorpamplona/amethyst/napplethost/NappletBrowserService.kt

@@ -161,6 +161,12 @@ class NappletBrowserService : Service() {
         configureWebView(wv)
         // Theme the pre-load background so a blank/loading page shows Amethyst's background, not white.
         wv.setBackgroundColor(bgColor)
+        // DIAGNOSTIC (scrolling): log whether touch input crosses the SurfaceControlViewHost boundary to
+        // the remote WebView at all. Returns false so it never consumes — the WebView still scrolls.
+        wv.setOnTouchListener { _, event ->
+            Log.w(TAG, "DIAG browser WebView touch action=${event.actionMasked} x=${event.x} y=${event.y}")
+            false
+        }
         wv.dropSystemBarInsets()
         applyWebViewProxy(if (useTor) proxyPort else -1)
         val shim = readContractAsset(NappletWebContract.SHIM_JS_PATH).decodeToString()