fix(studio): audit batch — debug.echo install, copyable errors, fast Diagnose

From a live-test audit:
- Install via the flow-editor 'Fix' sent 'debug.echo@^0' (version
  constraint included) as the install source; the hub resolves by bare
  name so it missed ('no store entry for debug.echo@^0'). Strip the
  @<constraint> like the Store page does — debug.echo now installs.
- Errors the operator could not copy: route the daemon-start failure
  (its stderr!), the flow-editor install failure and the federation
  issue failure through showFaiErrorSnack / a new showFaiProcessError
  helper, so every error is selectable, one-tap copyable and logged.
- Diagnose page opened slowly because doctor() Future.wait-ed on a live
  manifest fetch (8s server timeout); cap that one check at 2s so the
  page no longer waits on the network.

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

lib/pages/flows.dart

@@ -13,6 +13,7 @@
 import 'package:chain_studio_flow_editor/chain_studio_flow_editor.dart';
 import 'package:flutter/material.dart';
 
+import '../data/error_presentation.dart';
 import '../data/flow_run_driver.dart';
 import '../data/hub.dart';
 import '../l10n/app_localizations.dart';
@@ -94,7 +95,13 @@ class _FlowsPageState extends State<FlowsPage> {
   /// list so the editor can re-analyze without waiting for the
   /// parent widget rebuild.
   Future<List<String>?> _onInstallCapability(String capability) async {
-    return _runInstall(source: capability);
+    // The analyzer hands us the full `use:` value (e.g. `debug.echo@^0`).
+    // The hub resolves install sources by bare capability name; the
+    // `@<constraint>` suffix would make the store lookup miss ("no store
+    // entry for 'debug.echo@^0'"). Strip it — same as the Store page.
+    final at = capability.indexOf('@');
+    final bare = at < 0 ? capability : capability.substring(0, at);
+    return _runInstall(source: bare);
   }
 
   /// `Add source for <cap>…` handler. Prompts the operator
@@ -123,15 +130,13 @@ class _FlowsPageState extends State<FlowsPage> {
     } catch (e) {
       if (mounted) {
         final l = AppLocalizations.of(context);
-        final msg = l != null
-            ? l.installFailed(e.toString())
-            : 'Install failed: $e';
-        ScaffoldMessenger.of(context).removeCurrentSnackBar();
-        ScaffoldMessenger.of(context).showSnackBar(
-          SnackBar(
-            content: Text(msg),
-            behavior: SnackBarBehavior.floating,
-          ),
+        // Copyable error (was a plain SnackBar) — install failures
+        // carry the real cause (network, signature, store lookup).
+        showFaiErrorSnack(
+          context,
+          'flows.install',
+          e,
+          title: l != null ? l.installFailed('') : 'Install failed',
         );
       }
       return null;