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/main.dart

@@ -9,6 +9,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 
 import 'data/chain_log.dart';
+import 'data/error_presentation.dart';
 import 'data/hub.dart';
 import 'data/system_actions.dart';
 import 'data/theme_plugin.dart';
@@ -270,14 +271,21 @@ class StudioShellState extends State<StudioShell> {
     final l = AppLocalizations.of(context)!;
     final r = await SystemActions.chainDaemon(['start']);
     if (!mounted) return;
-    final detail = r.stderr.trim().isEmpty ? r.stdout.trim() : r.stderr.trim();
-    ScaffoldMessenger.of(context).showSnackBar(
-      SnackBar(
-        content: Text(
-          r.ok ? l.daemonStartRequested : l.daemonStartFailed(detail),
-        ),
-      ),
-    );
+    if (r.ok) {
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(content: Text(l.daemonStartRequested)),
+      );
+    } else {
+      // Surface the daemon's stderr/stdout as a copyable error — this
+      // is the message the operator most often needs to paste back.
+      showFaiProcessError(
+        context,
+        'daemon.start',
+        r.stdout,
+        r.stderr,
+        title: l.daemonStartFailed(''),
+      );
+    }
     // Probe again shortly so the UI flips to "connected" without
     // waiting for the next 5 s tick.
     Future.delayed(const Duration(seconds: 1), _checkHealth);
@@ -690,14 +698,21 @@ class _SidebarState extends State<_Sidebar>
     final l = AppLocalizations.of(context)!;
     final r = await SystemActions.chainDaemon(['start']);
     if (!context.mounted) return;
-    final detail = r.stderr.trim().isEmpty ? r.stdout.trim() : r.stderr.trim();
-    ScaffoldMessenger.of(context).showSnackBar(
-      SnackBar(
-        content: Text(
-          r.ok ? l.daemonStartRequested : l.daemonStartFailed(detail),
-        ),
-      ),
-    );
+    if (r.ok) {
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(content: Text(l.daemonStartRequested)),
+      );
+    } else {
+      // Surface the daemon's stderr/stdout as a copyable error — this
+      // is the message the operator most often needs to paste back.
+      showFaiProcessError(
+        context,
+        'daemon.start',
+        r.stdout,
+        r.stderr,
+        title: l.daemonStartFailed(''),
+      );
+    }
   }
 
   @override