Build the phone's APK as a signed release, and say so in the render report

The phone has been running the debug build: build-apk.sh assembled it, and
nothing in the app or its report said which build a frame time came from.
A debuggable build runs Compose at a fraction of release speed, so the
tuning so far was measured against the wrong number. On the emulator, the
same fixture and gestures: measure 1.4ms mean / 14.7ms worst on debug,
0.8ms / 6.6ms on release.

build-apk.sh now assembles the release variant, signed with a key it
generates once under ~/.config/ai-app (beside the pinned CA, outside any
checkout). The report's header names the build. The one native library is
declared kept-with-symbols so packaging stops warning about an NDK the
build does not need.

Also: ui-sandbox.sh keep now keeps the config too. The server appends
spawned sessions and enrolled tokens to it, so regenerating it left the
transcripts on disk and the registry empty.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

app/androidApp/src/main/kotlin/com/example/aiapp/SessionScreen.kt

@@ -1,5 +1,7 @@
 package com.example.aiapp
 
+import android.content.Context
+import android.content.pm.ApplicationInfo
 import android.os.Build
 import android.os.SystemClock
 import android.util.Log
@@ -1195,7 +1197,11 @@ fun SessionScreen(settings: ServerSettings, summary: SessionSummary, onBack: ()
                                 debugReport(
                                     device =
                                         "device: ${Build.MODEL} (${Build.MANUFACTURER})," +
-                                            " Android ${Build.VERSION.RELEASE}",
+                                            " Android ${Build.VERSION.RELEASE}\n" +
+                                            // A debuggable build runs Compose at a fraction of
+                                            // release speed, so a report that did not say which
+                                            // it came from was read as the app's own cost.
+                                            "build: ${if (debuggable(context)) "debug" else "release"}",
                                     transcript =
                                         listOf(
                                             "  ${items.size} events, ${rows.size} rows," +
@@ -2312,3 +2318,6 @@ private fun PickerButton(current: String, options: List<String>, onPick: (String
         }
     }
 }
+
+private fun debuggable(context: Context) =
+    context.applicationInfo.flags and ApplicationInfo.FLAG_DEBUGGABLE != 0