tools: beacon fixes — cleartext, multi-device, validated-net POST, status URL

Debugging against a real restricted LAN surfaced three fixes:
- Android blocks app cleartext HTTP by default (targetSdk 36) — the port
  discovery + reachability were fine (phone curl reached fmr), only the
  app POST was denied. Added usesCleartextTraffic for this dev tool.
- Multi-device: report + receiver are keyed by device (Build.MODEL) so a
  phone and tablet don't clobber each other; connector connects each.
- POST over a VALIDATED internet network (prefer cellular) since the
  wireless-debug wifi is often a restricted LAN.
- Status/notification now show the target beacon URL + which network, per
  the request to surface what it's connecting to.
Verified live: beacon tracks the (frequently rotating) port via mDNS and
self-reports the current endpoint within seconds.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

echolot-app/adb-beacon/src/main/AndroidManifest.xml

@@ -13,6 +13,7 @@
     <application
         android:allowBackup="false"
         android:label="Echolot ADB Beacon"
+        android:usesCleartextTraffic="true"
         android:theme="@android:style/Theme.Material.Light">
 
         <activity android:name=".MainActivity" android:exported="true">

echolot-app/adb-beacon/src/main/kotlin/app/echo_lot/adbbeacon/BeaconService.kt

@@ -90,9 +90,16 @@ class BeaconService : Service() {
         val ip = wifiIpv4() ?: run { Status.set("no wlan0 IPv4 (is wifi up?)"); return }
         val port = currentPort
         if (port <= 0) { Status.set("$ip — waiting for wireless-debug port"); return }
-        val body = """{"ip":"$ip","port":$port}"""
+        val device = android.os.Build.MODEL.replace(Regex("[^A-Za-z0-9_.-]"), "_")
+        val body = """{"device":"$device","ip":"$ip","port":$port}"""
+        // Send over a VALIDATED internet network — the wireless-debug wifi is often a restricted
+        // LAN with no real internet TCP egress, so bind the report to cellular/whatever actually
+        // reaches the beacon.
+        val net = internetNetwork()
         val ok = runCatching {
-            (URL(BuildConfig.BEACON_URL).openConnection() as HttpURLConnection).run {
+            val url = URL(BuildConfig.BEACON_URL)
+            val conn = (net?.openConnection(url) ?: url.openConnection()) as HttpURLConnection
+            conn.run {
                 requestMethod = "POST"
                 connectTimeout = 5000; readTimeout = 5000
                 doOutput = true
@@ -102,9 +109,40 @@ class BeaconService : Service() {
                 responseCode == 200
             }
         }.getOrDefault(false)
-        val line = if (ok) "reported $ip:$port ✓" else "report failed for $ip:$port (beacon unreachable?)"
+        val via = if (net != null) "via ${netLabel(net)}" else "via default net"
+        val line = if (ok) {
+            "reported [$device] $ip:$port ✓  $via\n→ ${BuildConfig.BEACON_URL}"
+        } else {
+            "report FAILED for [$device] $ip:$port  $via\n→ POST ${BuildConfig.BEACON_URL}"
+        }
         Status.set(line)
-        updateNotification(line)
+        updateNotification(if (ok) "reported $ip:$port ✓" else "report failed for $ip:$port")
+    }
+
+    /** A network with validated internet access, preferring cellular (the wireless-debug wifi is
+     *  frequently a restricted LAN that can't reach the beacon over TCP). */
+    private fun internetNetwork(): android.net.Network? {
+        val cm = getSystemService(Context.CONNECTIVITY_SERVICE) as android.net.ConnectivityManager
+        var fallback: android.net.Network? = null
+        for (n in cm.allNetworks) {
+            val c = cm.getNetworkCapabilities(n) ?: continue
+            if (!c.hasCapability(android.net.NetworkCapabilities.NET_CAPABILITY_INTERNET)) continue
+            if (!c.hasCapability(android.net.NetworkCapabilities.NET_CAPABILITY_VALIDATED)) continue
+            if (c.hasTransport(android.net.NetworkCapabilities.TRANSPORT_CELLULAR)) return n
+            fallback = n
+        }
+        return fallback
+    }
+
+    private fun netLabel(n: android.net.Network): String {
+        val cm = getSystemService(Context.CONNECTIVITY_SERVICE) as android.net.ConnectivityManager
+        val c = cm.getNetworkCapabilities(n) ?: return "net"
+        return when {
+            c.hasTransport(android.net.NetworkCapabilities.TRANSPORT_CELLULAR) -> "cellular"
+            c.hasTransport(android.net.NetworkCapabilities.TRANSPORT_WIFI) -> "wifi"
+            c.hasTransport(android.net.NetworkCapabilities.TRANSPORT_ETHERNET) -> "ethernet"
+            else -> "net"
+        }
     }
 
     /** The wlan0 (or first private) IPv4 the PC routes to. */