feat(graph): register the vault graph view in the context panel (T-323)

Wires GraphPanel into GraphExtension as the graph.view context-panel tab
(its icon-rail entry and tab id were already scaffolded) and ships the
builtin.graph i18n catalogs. The graph is now reachable: notes as nodes,
wikilinks as edges, hover-highlight and click-to-open. It activates after
its pql dependency, which supplies the link data.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -18,6 +18,10 @@ heading, and (b) bumping `pubspec.yaml` `version:` in the same commit.
 
 ### Added
 
+- **Vault graph view.** A force-directed link graph of the whole vault in the
+  context panel — notes are nodes, wikilinks edges. Hover highlights a note's
+  neighbourhood; click opens it in the editor. (T-323)
+
 ### Changed
 
 ### Fixed

assets/i18n/en_us/builtin.graph.json

@@ -0,0 +1,4 @@
+{
+  "tab.graph.title": { "translation": "Graph" },
+  "graph.empty": { "translation": "No linked notes in this vault." }
+}

assets/i18n/nl_nl/builtin.graph.json

@@ -0,0 +1,4 @@
+{
+  "tab.graph.title": { "translation": "Grafiek" },
+  "graph.empty": { "translation": "Geen gekoppelde notities in deze vault." }
+}

lib/builtin/graph/src/extension.dart

@@ -1,4 +1,7 @@
+import 'package:clide/builtin/graph/src/graph_panel.dart';
 import 'package:clide/extension/extension.dart';
+import 'package:clide/kernel/kernel.dart';
+import 'package:clide/widgets/widgets.dart';
 
 class GraphExtension extends ClideExtension {
   @override
@@ -11,5 +14,16 @@ class GraphExtension extends ClideExtension {
   List<String> get dependsOn => const ['builtin.pql'];
 
   @override
-  List<ContributionPoint> get contributions => const [];
+  List<ContributionPoint> get contributions => [
+    TabContribution(
+      id: 'graph.view',
+      slot: Slots.contextPanel,
+      title: 'Graph',
+      titleKey: 'tab.graph.title',
+      i18nNamespace: id,
+      icon: PhosphorIcons.byName('graph'),
+      priority: -70,
+      build: (_) => const GraphPanel(),
+    ),
+  ];
 }

test/builtin/graph/graph_extension_test.dart

@@ -0,0 +1,63 @@
+/// GraphExtension (T-323) contributes the vault-graph tab into the context
+/// panel — but only once its pql dependency is active (it reads link data
+/// through pql).
+library;
+
+import 'package:clide/builtin/graph/graph.dart';
+import 'package:clide/builtin/graph/src/graph_panel.dart';
+import 'package:clide/builtin/pql/pql.dart';
+import 'package:clide/extension/extension.dart';
+import 'package:clide/kernel/kernel.dart';
+import 'package:flutter/widgets.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import '../../helpers/kernel_fixture.dart';
+import '../../helpers/widget_harness.dart';
+
+void main() {
+  late KernelFixture f;
+  setUp(() async => f = await KernelFixture.create());
+  tearDown(() => f.dispose());
+
+  test('declares one context-panel tab with the graph.view identity', () {
+    final tabs = GraphExtension().contributions.whereType<TabContribution>().toList();
+    expect(tabs, hasLength(1));
+    final t = tabs.single;
+    expect(t.id, 'graph.view');
+    expect(t.slot, Slots.contextPanel);
+    expect(t.title, 'Graph');
+    expect(t.titleKey, 'tab.graph.title');
+    expect(t.i18nNamespace, 'builtin.graph');
+  });
+
+  testWidgets('the tab builds a GraphPanel', (tester) async {
+    final tab = GraphExtension().contributions.whereType<TabContribution>().single;
+    late Widget built;
+    await tester.pumpWidget(
+      anchoredHarness(
+        f,
+        Builder(
+          builder: (ctx) {
+            built = tab.build(ctx); // capture without mounting — no load/ipc needed
+            return const SizedBox();
+          },
+        ),
+      ),
+    );
+    expect(built, isA<GraphPanel>());
+  });
+
+  test('registers into the context panel once activated (after its pql dep)', () async {
+    f.services.extensions.register(PqlExtension());
+    f.services.extensions.register(GraphExtension());
+    await f.services.extensions.activate('builtin.pql');
+    await f.services.extensions.activate('builtin.graph');
+    expect(f.services.panels.tabsFor(Slots.contextPanel).any((t) => t.id == 'graph.view'), isTrue);
+  });
+
+  test('is skipped when its pql dependency is not active', () async {
+    f.services.extensions.register(GraphExtension());
+    await f.services.extensions.activate('builtin.graph'); // dep missing → skipped
+    expect(f.services.panels.tabsFor(Slots.contextPanel).any((t) => t.id == 'graph.view'), isFalse);
+  });
+}