prober: on-screen + in-report build number (versionCode, now 2)

Ascending integer bumped per deployed change; shown in the header and as
proberBuild in the JSON report so a report is attributable to an exact
build. buildConfig feature enabled for BuildConfig.VERSION_CODE.

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

echolot-prober/app/src/main/java/app/echo_lot/prober/export/Report.kt

@@ -7,6 +7,7 @@ import android.content.Context
 import android.content.Intent
 import android.os.Build
 import androidx.core.content.FileProvider
+import app.echo_lot.prober.BuildConfig
 import app.echo_lot.prober.probe.ProbeResult
 import kotlinx.serialization.Serializable
 import kotlinx.serialization.encodeToString
@@ -17,6 +18,9 @@ import java.io.File
 data class Report(
     val schema: String = "echolot/prober-report",
     val schemaVersion: String = "0.1.0",
+    // Ascending integer, bumped per deployed change (= versionCode). Shown on screen too, so a
+    // report and a screenshot are attributable to the same build.
+    val proberBuild: Int = BuildConfig.VERSION_CODE,
     val device: DeviceInfo,
     val results: List<ProbeResult>,
 )

echolot-prober/app/src/main/java/app/echo_lot/prober/ui/ProberScreen.kt

@@ -41,7 +41,10 @@ fun ProberScreen(
     onShare: () -> Unit,
 ) {
     Column(Modifier.fillMaxSize().padding(16.dp)) {
-        Text("Echolot Capability Prober", style = MaterialTheme.typography.headlineSmall)
+        Text(
+            "Echolot Capability Prober · build ${app.echo_lot.prober.BuildConfig.VERSION_CODE}",
+            style = MaterialTheme.typography.headlineSmall,
+        )
         Text(
             "Runs the borderline no-root probes from the feasibility matrix on THIS device and reports what actually works.",
             style = MaterialTheme.typography.bodySmall,