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/data/error_presentation.dart

@@ -85,6 +85,30 @@ void showFaiErrorSnack(
   );
 }
 
+/// Surface a failed external-process result (daemon start, binary
+/// probe, file-open) as a copyable error snack. The `ok/stdout/stderr`
+/// record these actions return is not a thrown error, so call sites used
+/// to drop it into a raw `SnackBar(Text(...))` — uncopyable, the exact
+/// thing the operator needs to paste back. This joins stderr + stdout
+/// into one selectable, one-tap-copyable, logged message.
+void showFaiProcessError(
+  BuildContext context,
+  String source,
+  String stdout,
+  String stderr, {
+  String? title,
+}) {
+  final detail = [stderr.trim(), stdout.trim()]
+      .where((s) => s.isNotEmpty)
+      .join('\n\n');
+  showFaiErrorSnack(
+    context,
+    source,
+    detail.isEmpty ? 'process exited non-zero (no output)' : detail,
+    title: title,
+  );
+}
+
 /// Show [error] as a centered modal dialog. Use this when the
 /// failure blocks meaningful interaction (auth missing, hub
 /// unreachable) — a SnackBar would be too easy to dismiss.