fix(docs): page help buttons open the right topic + wiring guard

The Federation and Runs help buttons opened the architecture doc:
federation.md/runs.md existed as assets but had no _DocEntry, so
showFaiDoc resolved the unknown slug to _kDocs.first. Register both
(onWelcome: false, so they don't clutter the newcomer grid but are
reachable), split the Welcome grid onto the curated subset, and make
the unknown-slug fallback assert in debug instead of silently opening
the wrong topic.

Guard (no-bugfix-without-a-guard): doc_help_wiring_test.dart scans
lib/ for every showFaiDoc('slug') call and asserts each has a
registered entry AND both assets/docs/<slug>[_de].md files. Exposes
kKnownDocSlugs for the test.

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

lib/l10n/app_localizations_en.dart

@@ -181,6 +181,20 @@ class AppLocalizationsEn extends AppLocalizations {
   String get welcomeDocApprovalsBlurb =>
       'Human-in-the-loop checkpoints — when to use them, how the audit log records them.';
 
+  @override
+  String get welcomeDocFederationTitle => 'Federation';
+
+  @override
+  String get welcomeDocFederationBlurb =>
+      'Connect other hubs (satellites) so their capabilities become usable here — what a satellite is and how enrolment works.';
+
+  @override
+  String get welcomeDocRunsTitle => 'Background runs';
+
+  @override
+  String get welcomeDocRunsBlurb =>
+      'Flows that keep working in the background — what they are for, how to switch the feature on and monitor the runs.';
+
   @override
   String get helpTooltip => 'Help';
 
@@ -338,6 +352,9 @@ class AppLocalizationsEn extends AppLocalizations {
   @override
   String get buttonCancel => 'Cancel';
 
+  @override
+  String get buttonLearnMore => 'Learn more';
+
   @override
   String get buttonSave => 'Save';
 
@@ -3159,6 +3176,14 @@ class AppLocalizationsEn extends AppLocalizations {
   @override
   String get federationNameLabel => 'Satellite name';
 
+  @override
+  String get federationAddIntro =>
+      'A satellite is another hub this hub connects to — its capabilities then become usable here in flows. You give it a name and receive a one-time token the satellite uses to enrol with this hub.';
+
+  @override
+  String get federationNameHelp =>
+      'A free-form name to recognize this satellite in the list (e.g. its location or purpose). Display only — it changes nothing technical.';
+
   @override
   String get federationIssueButton => 'Issue';