add decision detail view in context panel via MessageBus

Click a decision card in the sidebar → publishes on
builtin.decisions/selection → detail view loads full record →
context panel activates decisions.detail tab and renders:
- Type dot with tooltip, ID colored by type, domain badge
- Title, date
- Status badge for resolved questions

Same MessageBus pattern as ticket detail.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/builtin/decisions/src/extension.dart

@@ -1,3 +1,4 @@
+import 'package:clide/builtin/decisions/src/decision_detail_view.dart';
 import 'package:clide/builtin/decisions/src/decisions_view.dart';
 import 'package:clide/extension/extension.dart';
 import 'package:clide/kernel/kernel.dart';
@@ -8,7 +9,7 @@ class DecisionsExtension extends ClideExtension {
   @override
   String get title => 'Decisions';
   @override
-  String get version => '0.1.0';
+  String get version => '0.2.0';
   @override
   List<String> get dependsOn => const [];
 
@@ -23,5 +24,12 @@ class DecisionsExtension extends ClideExtension {
           priority: -20,
           build: (_) => const DecisionsView(),
         ),
+        TabContribution(
+          id: 'decisions.detail',
+          slot: Slots.contextPanel,
+          title: 'Decision',
+          priority: -50,
+          build: (_) => const DecisionDetailView(),
+        ),
       ];
 }