wire decisions, tickets, markdown viewer, and graph extensions

Four stub extensions now contribute real tabs with views:

- Decisions panel (sidebar, priority -20): lists confirmed D-records
  from pql decisions list with ID, title, and domain.
- Tickets panel (sidebar, priority -10): lists tickets with status
  dot color-coded by state (done=green, in_progress=blue,
  cancelled=red).
- Markdown viewer (context, priority -100): shows raw content of
  the active .md file, listens for editor.buffer_activated events.
- Graph view (context, priority -80): lists files with inbound and
  outbound link counts from pql search --connections.

All four fetch data via the daemon's pql.exec IPC surface.

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

app/lib/builtin/markdown/src/extension.dart

@@ -1,17 +1,27 @@
+import 'package:clide_app/builtin/markdown/src/markdown_viewer.dart';
 import 'package:clide_app/extension/extension.dart';
+import 'package:clide_app/kernel/kernel.dart';
 
-/// Tier-0 stub. Real implementation lands in a later tier; the extension
-/// is registered so the extensions-ui surface can list it as "installed,
-/// not yet implemented" and its id is reserved.
 class MarkdownExtension extends ClideExtension {
   @override
   String get id => 'builtin.markdown';
   @override
   String get title => 'Markdown';
   @override
-  String get version => '0.0.0-stub';
+  String get version => '0.1.0';
   @override
   List<String> get dependsOn => const ['builtin.editor'];
+
   @override
-  List<ContributionPoint> get contributions => const [];
+  List<ContributionPoint> get contributions => [
+        TabContribution(
+          id: 'markdown.viewer',
+          slot: Slots.contextPanel,
+          title: 'Viewer',
+          titleKey: 'tab.viewer',
+          i18nNamespace: id,
+          priority: -100,
+          build: (_) => const MarkdownViewer(),
+        ),
+      ];
 }

app/lib/builtin/markdown/src/markdown_viewer.dart

@@ -0,0 +1,94 @@
+import 'dart:async';
+
+import 'package:clide_app/kernel/kernel.dart';
+import 'package:clide_app/widgets/widgets.dart';
+import 'package:flutter/widgets.dart';
+
+class MarkdownViewer extends StatefulWidget {
+  const MarkdownViewer({super.key});
+
+  @override
+  State<MarkdownViewer> createState() => _MarkdownViewerState();
+}
+
+class _MarkdownViewerState extends State<MarkdownViewer> {
+  String? _path;
+  String? _content;
+  String? _error;
+  StreamSubscription<DaemonEvent>? _eventSub;
+
+  @override
+  void didChangeDependencies() {
+    super.didChangeDependencies();
+    if (_eventSub != null) return;
+    final kernel = ClideKernel.of(context);
+    _eventSub = kernel.events.on<DaemonEvent>().listen((e) {
+      if (e.kind == 'editor.buffer_activated') {
+        final path = e.data['path'] as String?;
+        if (path != null && path.endsWith('.md')) {
+          _loadFile(path);
+        }
+      }
+    });
+    final activeTab = kernel.panels.activeTabIn(Slots.workspace);
+    if (activeTab == 'editor.active') {
+      unawaited(_loadActiveBuffer());
+    }
+  }
+
+  @override
+  void dispose() {
+    _eventSub?.cancel();
+    super.dispose();
+  }
+
+  Future<void> _loadActiveBuffer() async {
+    final kernel = ClideKernel.of(context);
+    final resp = await kernel.ipc.request('editor.active');
+    if (!mounted || !resp.ok) return;
+    final path = resp.data['path'] as String?;
+    if (path != null && path.endsWith('.md')) {
+      await _loadFile(path);
+    }
+  }
+
+  Future<void> _loadFile(String path) async {
+    final kernel = ClideKernel.of(context);
+    final resp = await kernel.ipc.request('files.read', args: {'path': path});
+    if (!mounted) return;
+    if (resp.ok) {
+      setState(() {
+        _path = path;
+        _content = resp.data['content'] as String? ?? '';
+        _error = null;
+      });
+    } else {
+      setState(() => _error = resp.error?.message);
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    if (_error != null) {
+      return Padding(padding: const EdgeInsets.all(12), child: ClideText(_error!, muted: true));
+    }
+    if (_content == null) {
+      return const Padding(
+        padding: EdgeInsets.all(12),
+        child: ClideText('Open a .md file to preview it here.', muted: true),
+      );
+    }
+    final tokens = ClideTheme.of(context).surface;
+    return ClidePaneChrome(
+      title: _path ?? 'viewer',
+      subtitle: '${_content!.split('\n').length} lines',
+      child: SingleChildScrollView(
+        padding: const EdgeInsets.all(12),
+        child: Text(
+          _content!,
+          style: TextStyle(color: tokens.globalForeground, fontSize: 13, fontFamily: clideMonoFamily, fontFamilyFallback: clideMonoFamilyFallback),
+        ),
+      ),
+    );
+  }
+}