Add app source and tests

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

lib/Peach/about/internal/application/StepTracker.dart

@@ -0,0 +1,104 @@
+import 'dart:async';
+
+enum StepState { pending, active, done, failed, skipped }
+
+class DeployStep {
+  final String key;
+  final String label;
+  StepState state;
+  double? progress; // 0..1 within this step, when meaningful
+
+  DeployStep(
+    this.key,
+    this.label, {
+    this.state = StepState.pending,
+    this.progress,
+  });
+}
+
+/// Tracks an ordered list of steps for a build or deploy operation and streams
+/// updates so the UI can render a live stepper with per-step progress.
+class StepTracker {
+  final _controller = StreamController<List<DeployStep>>.broadcast();
+  Stream<List<DeployStep>> get stream => _controller.stream;
+  final List<DeployStep> steps = [];
+
+  void reset(List<(String, String)> defs) {
+    steps
+      ..clear()
+      ..addAll(defs.map((d) => DeployStep(d.$1, d.$2)));
+    _emit();
+  }
+
+  DeployStep? _find(String key) {
+    for (final s in steps) {
+      if (s.key == key) return s;
+    }
+    return null;
+  }
+
+  void active(String key) {
+    final s = _find(key);
+    if (s == null) return;
+    // mark earlier active/pending steps done as we move forward
+    for (final step in steps) {
+      if (step == s) break;
+      if (step.state == StepState.active) step.state = StepState.done;
+    }
+    s.state = StepState.active;
+    s.progress = null;
+    _emit();
+  }
+
+  void progress(String key, double? p) {
+    final s = _find(key);
+    if (s == null) return;
+    s.progress = p;
+    _emit();
+  }
+
+  void done(String key) => _set(key, StepState.done);
+  void fail(String key) => _set(key, StepState.failed);
+  void skip(String key) => _set(key, StepState.skipped);
+
+  void _set(String key, StepState state) {
+    final s = _find(key);
+    if (s == null) return;
+    s.state = state;
+    s.progress = null;
+    _emit();
+  }
+
+  /// Marks the currently-active step done (used before moving on).
+  void completeActive() {
+    for (final s in steps) {
+      if (s.state == StepState.active) s.state = StepState.done;
+    }
+    _emit();
+  }
+
+  /// Any still-pending/active steps become failed (on an error).
+  void failRemaining() {
+    for (final s in steps) {
+      if (s.state == StepState.active) {
+        s.state = StepState.failed;
+      } else if (s.state == StepState.pending) {
+        s.state = StepState.skipped;
+      }
+    }
+    _emit();
+  }
+
+  void clear() {
+    steps.clear();
+    _emit();
+  }
+
+  void _emit() {
+    if (!_controller.isClosed) {
+      _controller.add(List.unmodifiable(steps));
+    }
+  }
+
+  void dispose() => _controller.close();
+}