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/hub.dart

@@ -902,7 +902,18 @@ class HubService {
           .catchError((_) => <PendingApprovalEntry>[]),
       _client.verifyEventChain().catchError((_) => VerifyEventChainResponse()),
       _client.listServices().catchError((_) => <DeclaredService>[]),
-      _client.checkUpdate().catchError((_) => CheckUpdateResponse()),
+      // checkUpdate does a live manifest fetch (server-side 8s timeout).
+      // The other five are local-socket RPCs that return in ms, so cap
+      // this one tightly — otherwise it alone gates the whole Diagnose
+      // page open. A timeout reads as "release host unreachable", which
+      // the UI already renders as an offline banner, not an error.
+      _client
+          .checkUpdate()
+          .timeout(
+            const Duration(seconds: 2),
+            onTimeout: () => CheckUpdateResponse(),
+          )
+          .catchError((_) => CheckUpdateResponse()),
       _client.daemonPaths().catchError((_) => DaemonPathsResponse()),
     ]);