feat: HubClient.listFlows + runSavedFlow

Two more wrappers for Studio's new Flows page. Saved flows can
be listed (FlowSummary: name + path + size) and executed by
name with a map of named text inputs. Returns a SubmitResponse
whose `outputs` map carries the flow's declared outputs as
Payloads.

Common payload type re-exposed via the `Payload` typedef from
common.pb.dart so the Studio side can pattern-match on
text/json/bytes/file without dragging in proto imports.

Bumps fai_dart_sdk 0.4.0 -> 0.5.0.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

lib/src/hub_client.dart

@@ -6,6 +6,7 @@
 
 import 'package:grpc/grpc.dart';
 
+import 'generated/fai/v1/common.pb.dart' as pb_common;
 import 'generated/fai/v1/hub.pb.dart' as pb;
 import 'generated/fai/v1/hub.pbgrpc.dart' as grpc_hub;
 import 'generated/google/protobuf/empty.pb.dart' show Empty;
@@ -41,6 +42,9 @@ typedef PendingApprovalEntry = pb.PendingApprovalEntry;
 typedef DeclaredService = pb.DeclaredService;
 typedef VerifyEventChainResponse = pb.VerifyEventChainResponse;
 typedef ModuleInfoResponse = pb.ModuleInfoResponse;
+typedef FlowSummary = pb.FlowSummary;
+typedef Payload = pb_common.Payload;
+typedef SubmitResponse = pb.SubmitResponse;
 
 /// Typed client for the F∆I Hub gRPC surface. Construct once,
 /// reuse for the process lifetime, call [close] on shutdown.
@@ -159,6 +163,29 @@ class HubClient {
     return r.services;
   }
 
+  /// All saved flows known to the hub. Each entry carries the
+  /// flow name, on-disk path and byte size.
+  Future<List<FlowSummary>> listFlows() async {
+    final r = await _admin.listFlows(Empty());
+    return r.flows;
+  }
+
+  /// Run a saved flow by name with the supplied named inputs.
+  /// Each input value is wrapped as a text Payload — the most
+  /// common case for human-driven runs from Studio. Callers
+  /// that need bytes / file payloads use the lower-level
+  /// SubmitRequest path.
+  Future<SubmitResponse> runSavedFlow({
+    required String name,
+    required Map<String, String> textInputs,
+  }) async {
+    final req = pb.RunSavedFlowRequest()..name = name;
+    for (final entry in textInputs.entries) {
+      req.inputs[entry.key] = pb_common.Payload()..text = entry.value;
+    }
+    return _admin.runSavedFlow(req);
+  }
+
   /// Closes the gRPC channel. Idempotent.
   Future<void> close() async {
     await _channel.shutdown();