feat(studio): @-syntax file inputs in flows, copyable doc errors, services-row overflow (v0.40.0)

Three concrete fixes against today's user feedback.

- Flows that take binary inputs (extract / extract-summarize /
  …) work from the Flows tab. The run-flow input dialog now
  accepts the same `@/path/to/file` syntax `fai run --input`
  uses on the CLI: any value beginning with `@` is read as
  bytes and sent as a binary Payload; plain values still flow
  through as text. The dialog hint copy and the example
  placeholder reflect the new syntax. File-read failures
  surface as a SnackBar before the run dialog opens, so a
  typo in the path doesn't reach the hub. Threaded through
  `_FlowRunDialog` and `HubService.runSavedFlow`, which both
  carry separate `textInputs` and `fileInputs` maps now and
  forward to the SDK's mixed-mode runSavedFlow (v0.14.0).

- The Welcome doc-reader's error path uses `FaiErrorBox` so
  the actual underlying error is selectable + copy-to-
  clipboard via the existing widget. Plus the loader throws
  a richer error string that names *both* attempted asset
  paths (`<slug>_<lang>.md` and the EN fallback) and the
  underlying exception each, so the operator can paste a
  diagnostic into a chat without us having to ship a
  separate "how to read Flutter asset errors" doc.

- Doctor's empty Services panel had a horizontal RenderFlex
  overflow at narrow widths because the long mono-spaced
  hint ("add to ~/.fai/config.yaml under services:") and
  the leading icon+text both demanded full intrinsic width
  in a single Row. Now wraps via a `Wrap` widget so the
  hint flows to a second line on narrow viewports and stays
  in the same row when there's space.

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

lib/pages/flows.dart

@@ -1,3 +1,6 @@
+import 'dart:io';
+import 'dart:typed_data';
+
 import 'package:flutter/material.dart';
 
 import '../data/hub.dart';
@@ -29,11 +32,44 @@ class _FlowsPageState extends State<FlowsPage> {
   Future<void> _runFlow(SavedFlow flow) async {
     final inputs = await _FlowInputDialog.show(context, flow);
     if (inputs == null) return;
+    // Split the dialog's text-shaped key=value pairs into text
+    // vs file payloads. Values starting with `@` mean "treat
+    // the rest as a path; read the file as bytes" — same
+    // syntax `fai run --input` uses on the CLI. File-read
+    // failures bubble up as the run dialog's error state so
+    // the operator sees a useful message.
+    final textInputs = <String, String>{};
+    final fileInputs = <String, Uint8List>{};
+    String? readError;
+    for (final entry in inputs.entries) {
+      final value = entry.value;
+      if (value.startsWith('@')) {
+        final path = value.substring(1).trim();
+        try {
+          fileInputs[entry.key] = await File(path).readAsBytes();
+        } catch (e) {
+          readError = '${entry.key}: $e';
+          break;
+        }
+      } else {
+        textInputs[entry.key] = value;
+      }
+    }
     if (!mounted) return;
+    if (readError != null) {
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(content: Text(readError)),
+      );
+      return;
+    }
     showDialog<void>(
       context: context,
       barrierDismissible: false,
-      builder: (_) => _FlowRunDialog(flow: flow, inputs: inputs),
+      builder: (_) => _FlowRunDialog(
+        flow: flow,
+        textInputs: textInputs,
+        fileInputs: fileInputs,
+      ),
     );
   }
 
@@ -248,9 +284,14 @@ class _FlowInputDialogState extends State<_FlowInputDialog> {
 
 class _FlowRunDialog extends StatefulWidget {
   final SavedFlow flow;
-  final Map<String, String> inputs;
+  final Map<String, String> textInputs;
+  final Map<String, Uint8List> fileInputs;
 
-  const _FlowRunDialog({required this.flow, required this.inputs});
+  const _FlowRunDialog({
+    required this.flow,
+    required this.textInputs,
+    required this.fileInputs,
+  });
 
   @override
   State<_FlowRunDialog> createState() => _FlowRunDialogState();
@@ -264,7 +305,8 @@ class _FlowRunDialogState extends State<_FlowRunDialog> {
     super.initState();
     _future = HubService.instance.runSavedFlow(
       name: widget.flow.name,
-      textInputs: widget.inputs,
+      textInputs: widget.textInputs,
+      fileInputs: widget.fileInputs,
     );
   }