sidebar focus indicators, bus navigation, font constants

All sidebar and detail panes use clideFontSmall/clideFontBadge/
clideFontCaption instead of hardcoded sizes — single place to tune.

Decision detail view subscribes to the message bus for selection
events (same pattern as ticket controller) and publishes focus after
loading.  Both decisions and tickets sidebar views subscribe to the
focus channel, expand the accordion section, highlight the active
card, and scroll it into view.

Clickable DQRT links wired in decision detail, ticket detail, and
markdown viewer via onRecordTap.  Ticket descriptions now render
through ClideMarkdown instead of plain text.

Co-Authored-By: Claude <noreply@anthropic.com>

lib/builtin/markdown/src/markdown_viewer.dart

@@ -67,6 +67,15 @@ class _MarkdownViewerState extends State<MarkdownViewer> {
     }
   }
 
+  void _navigateToRecord(BuildContext context, String id) {
+    final kernel = ClideKernel.of(context);
+    if (id.startsWith('T-')) {
+      kernel.messages.publish('builtin.tickets', 'selection', {'id': id});
+    } else {
+      kernel.messages.publish('builtin.decisions', 'selection', {'id': id});
+    }
+  }
+
   @override
   Widget build(BuildContext context) {
     if (_error != null) {
@@ -83,7 +92,7 @@ class _MarkdownViewerState extends State<MarkdownViewer> {
       subtitle: '${_content!.split('\n').length} lines',
       child: SingleChildScrollView(
         padding: const EdgeInsets.all(12),
-        child: ClideMarkdown(_content!),
+        child: ClideMarkdown(_content!, onRecordTap: (id) => _navigateToRecord(context, id)),
       ),
     );
   }