feat(ble): Phase 2 BLE file transfer protocol

asg_client/app/src/debug/AndroidManifest.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools">
+
+    <application>
+        <!-- Allow adb shell am broadcast to reach BleTransferMode in debug builds. -->
+        <receiver
+            android:name="com.mentra.asg_client.io.bluetooth.managers.BleTransferModeReceiver"
+            android:exported="true"
+            tools:replace="android:exported" />
+    </application>
+</manifest>

asg_client/app/src/main/AndroidManifest.xml

@@ -198,6 +198,16 @@
             </intent-filter>
         </receiver>
 
+        <!-- Debug: exported via src/debug/AndroidManifest.xml for adb toggles -->
+        <receiver
+            android:name="com.mentra.asg_client.io.bluetooth.managers.BleTransferModeReceiver"
+            android:enabled="true"
+            android:exported="false">
+            <intent-filter>
+                <action android:name="com.mentra.BLE_TRANSFER_MODE" />
+            </intent-filter>
+        </receiver>
+
         <!-- Intent IPC receiver for third-party app commands -->
         <receiver
             android:name="com.mentra.asg_client.receiver.IntentCommandReceiver"

asg_client/app/src/main/java/com/mentra/asg_client/io/bluetooth/managers/BlePhotoReadyAck.java

@@ -0,0 +1,60 @@
+package com.mentra.asg_client.io.bluetooth.managers;
+
+import android.util.Log;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Synchronizes ASG {@code ble_photo_ready} transmission with phone {@code ble_ready_ack} so file
+ * packets start only after the JSON notification has reached the phone (Phase 2).
+ */
+public final class BlePhotoReadyAck {
+
+    private static final String TAG = "BlePhotoReadyAck";
+    private static final ConcurrentHashMap<String, CountDownLatch> LATCHES =
+            new ConcurrentHashMap<>();
+
+    private BlePhotoReadyAck() {}
+
+    public static void prepare(String requestId) {
+        if (requestId == null || requestId.isEmpty()) {
+            return;
+        }
+        LATCHES.put(requestId, new CountDownLatch(1));
+    }
+
+    public static boolean await(String requestId, long timeoutMs) {
+        if (requestId == null || requestId.isEmpty()) {
+            return false;
+        }
+        CountDownLatch latch = LATCHES.get(requestId);
+        if (latch == null) {
+            return false;
+        }
+        try {
+            boolean signaled = latch.await(timeoutMs, TimeUnit.MILLISECONDS);
+            if (!signaled) {
+                Log.w(TAG, "ble_ready_ack timeout for requestId=" + requestId);
+            }
+            return signaled;
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+            Log.w(TAG, "ble_ready_ack wait interrupted for requestId=" + requestId);
+            return false;
+        } finally {
+            LATCHES.remove(requestId);
+        }
+    }
+
+    public static void signal(String requestId) {
+        if (requestId == null || requestId.isEmpty()) {
+            return;
+        }
+        CountDownLatch latch = LATCHES.remove(requestId);
+        if (latch != null) {
+            latch.countDown();
+            Log.i(TAG, "ble_ready_ack received for requestId=" + requestId);
+        }
+    }
+}

asg_client/app/src/main/java/com/mentra/asg_client/io/bluetooth/managers/BleTransferModeReceiver.java

@@ -0,0 +1,21 @@
+package com.mentra.asg_client.io.bluetooth.managers;
+
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+import com.mentra.asg_client.BuildConfig;
+
+/**
+ * Manifest-registered receiver so {@code adb shell am broadcast} can toggle {@link
+ * BleTransferMode} in debug builds. No-op in release.
+ */
+public class BleTransferModeReceiver extends BroadcastReceiver {
+
+    @Override
+    public void onReceive(Context context, Intent intent) {
+        if (!BuildConfig.DEBUG) {
+            return;
+        }
+        BleTransferMode.handleIntent(intent);
+    }
+}