Add app source and tests

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

lib/Peach/see/kafka/ConnectKafka.dart

@@ -0,0 +1,36 @@
+import '../../about/external/data/Kafka.dart';
+
+/// One scan's worth of cluster state.
+class KafkaScan {
+  final List<KafkaTopic> topics;
+  final List<KafkaConsumerGroup> groups;
+  final KafkaCluster cluster;
+
+  const KafkaScan({
+    required this.topics,
+    required this.groups,
+    required this.cluster,
+  });
+
+  /// Nothing came back at all — usually an unreachable bootstrap server rather
+  /// than a genuinely empty cluster.
+  bool get isEmpty =>
+      topics.isEmpty && groups.isEmpty && cluster.brokers.isEmpty;
+}
+
+abstract class ConnectKafka {
+  /// Whether the Kafka CLI tools were found, and where.
+  void onKafkaDetected(KafkaStatus status);
+
+  /// Detection itself failed (the server couldn't be probed).
+  void onDetectFailed(String message);
+
+  /// Topics, groups and cluster health, freshly read.
+  void onScanned(KafkaScan scan);
+
+  /// The scan failed.
+  void onScanFailed(String message);
+
+  /// Output of the broker probe, to show in a sheet.
+  void onProbeOutput(String title, String output);
+}

lib/Peach/see/kafka/Kafka.dart

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+import 'package:flutter/cupertino.dart';
+
+import '../../about/internal/application/ServerProfile.dart';
+import 'KafkaState.dart';
+
+/// Live Kafka monitoring over SSH: topics with message offsets, consumer
+/// groups with lag, and cluster/broker health. Everything comes from the
+/// standard Kafka CLI tools run on the server.
+class Kafka extends StatefulWidget {
+  final ServerProfile server;
+
+  const Kafka({super.key, required this.server});
+
+  @override
+  State<Kafka> createState() => KafkaState();
+}

lib/Peach/see/kafka/ViewKafka.dart

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+import '../../about/internal/application/ServerProfile.dart';
+import '../parent/ParentViewModel.dart';
+import 'ConnectKafka.dart';
+
+class ViewKafka extends ParentViewModel {
+  ConnectKafka connection;
+
+  ViewKafka(super.context, this.connection);
+
+  /// Looks for the Kafka CLI tools on PATH and in the usual install dirs.
+  void detectKafka(ServerProfile server) async {
+    if (!await canReach(server, () => detectKafka(server))) return;
+    try {
+      final status = await getDataManager().kafkaDetect(server);
+      connection.onKafkaDetected(status);
+    } catch (error) {
+      connection.onDetectFailed(error.toString());
+    }
+  }
+
+  /// Reads topics, consumer groups and cluster health in one pass. They're
+  /// three separate CLI invocations, so this is where they're sequenced.
+  void scan(
+    ServerProfile server, {
+    required String binDir,
+    required String suffix,
+    required String bootstrap,
+    required bool includeInternal,
+  }) async {
+    try {
+      final topics = await getDataManager().kafkaTopics(
+        server,
+        binDir: binDir,
+        suffix: suffix,
+        bootstrap: bootstrap,
+        includeInternal: includeInternal,
+      );
+      final groups = await getDataManager().kafkaGroups(
+        server,
+        binDir: binDir,
+        suffix: suffix,
+        bootstrap: bootstrap,
+      );
+      final cluster = await getDataManager().kafkaCluster(
+        server,
+        binDir: binDir,
+        suffix: suffix,
+        bootstrap: bootstrap,
+      );
+
+      connection.onScanned(
+        KafkaScan(topics: topics, groups: groups, cluster: cluster),
+      );
+    } catch (error) {
+      connection.onScanFailed(error.toString());
+    }
+  }
+
+  /// Runs `kafka-broker-api-versions` so the user can see exactly what the
+  /// broker says when a scan comes back empty.
+  void probeBroker(
+    ServerProfile server, {
+    required String binDir,
+    required String suffix,
+    required String bootstrap,
+  }) async {
+    showLoading("Probing $bootstrap …");
+    try {
+      final output = await getDataManager().kafkaTest(
+        server,
+        binDir: binDir,
+        suffix: suffix,
+        bootstrap: bootstrap,
+      );
+      closeLoading();
+      connection.onProbeOutput(
+        'kafka-broker-api-versions · $bootstrap',
+        output.isEmpty ? '(no output — broker unreachable?)' : output,
+      );
+    } catch (error) {
+      handleError(
+        error,
+        () => probeBroker(
+          server,
+          binDir: binDir,
+          suffix: suffix,
+          bootstrap: bootstrap,
+        ),
+        () {},
+        "Retry",
+      );
+    }
+  }
+}