clickable file references in the Claude conversation (T-300)

Workspace file paths mentioned by Claude now linkify and open in the
editor: bare (lib/app.dart), with a line (lib/app.dart:42), backticked,
or as markdown links. Only paths that exist in the repo linkify — the
resolver gates on existence so prose (version numbers, "e.g.") stays
literal. Clicking maps to the editor.open verb, jumping to the line when
a :line suffix is present (D-6 parity).

ClideMarkdown gains resolveFileRef + onOpenFile hooks; conversation_view
resolves against the open project root + existsSync and dispatches over
IPC. Detection covers running prose, whole-content code spans, and link
hrefs.

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

test/widgets/src/clide_markdown_file_ref_test.dart

@@ -0,0 +1,128 @@
+/// Tests for ClideMarkdown workspace file references (T-300): paths that the
+/// resolver confirms exist become clickable and open in the editor; everything
+/// else stays literal. The resolver is stubbed so no real filesystem is touched.
+library;
+
+import 'package:clide/widgets/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());
+
+  // Resolves only the one known repo path; everything else is "not a file".
+  String? resolve(String p) => p == 'lib/app.dart' ? '/repo/lib/app.dart' : null;
+
+  ClideMarkdown md(String src, {void Function(String, int?)? onOpen}) => ClideMarkdown(
+        src,
+        resolveFileRef: resolve,
+        onOpenFile: onOpen ?? (_, __) {},
+      );
+
+  testWidgets('a bare repo path in prose is tappable and opens with no line', (tester) async {
+    String? path;
+    int? line = -1;
+    await tester.pumpWidget(harness(f, md('see lib/app.dart for the entry point', onOpen: (p, l) {
+      path = p;
+      line = l;
+    })));
+    await tester.pump();
+
+    await tester.tap(find.text('lib/app.dart'));
+    await tester.pump();
+    expect(path, '/repo/lib/app.dart');
+    expect(line, isNull);
+  });
+
+  testWidgets('a path:line ref opens at the line', (tester) async {
+    String? path;
+    int? line;
+    await tester.pumpWidget(harness(f, md('crash at lib/app.dart:42 today', onOpen: (p, l) {
+      path = p;
+      line = l;
+    })));
+    await tester.pump();
+
+    await tester.tap(find.text('lib/app.dart:42'));
+    await tester.pump();
+    expect(path, '/repo/lib/app.dart');
+    expect(line, 42);
+  });
+
+  testWidgets('a path:line:col ref opens at the line, ignoring the column', (tester) async {
+    int? line;
+    await tester.pumpWidget(harness(f, md('lib/app.dart:42:8', onOpen: (_, l) => line = l)));
+    await tester.pump();
+
+    await tester.tap(find.text('lib/app.dart:42:8'));
+    await tester.pump();
+    expect(line, 42);
+  });
+
+  testWidgets('a backticked path is clickable', (tester) async {
+    String? path;
+    int? line;
+    await tester.pumpWidget(harness(f, md('open `lib/app.dart:7`', onOpen: (p, l) {
+      path = p;
+      line = l;
+    })));
+    await tester.pump();
+
+    await tester.tap(find.text('lib/app.dart:7'));
+    await tester.pump();
+    expect(path, '/repo/lib/app.dart');
+    expect(line, 7);
+  });
+
+  testWidgets('a markdown [text](path) link opens the resolved href file', (tester) async {
+    String? path;
+    await tester.pumpWidget(harness(f, md('[the app](lib/app.dart)', onOpen: (p, _) => path = p)));
+    await tester.pump();
+
+    await tester.tap(find.text('the app'));
+    await tester.pump();
+    expect(path, '/repo/lib/app.dart');
+  });
+
+  testWidgets('a path that does not resolve stays literal (no link, no fire)', (tester) async {
+    var calls = 0;
+    await tester.pumpWidget(harness(f, md('nothing at lib/ghost.dart here', onOpen: (_, __) => calls++)));
+    await tester.pumpAndSettle();
+
+    // Rendered as plain text — tapping it does nothing.
+    await tester.tap(find.textContaining('lib/ghost.dart'), warnIfMissed: false);
+    await tester.pump();
+    expect(calls, 0);
+  });
+
+  testWidgets('dotted prose (a version number) does not linkify', (tester) async {
+    var calls = 0;
+    await tester.pumpWidget(harness(f, md('shipped version 2.2.0 today', onOpen: (_, __) => calls++)));
+    await tester.pumpAndSettle();
+
+    await tester.tap(find.textContaining('2.2.0'), warnIfMissed: false);
+    await tester.pump();
+    expect(calls, 0);
+  });
+
+  testWidgets('with no file hooks, a path renders inert (no crash)', (tester) async {
+    await tester.pumpWidget(harness(f, const ClideMarkdown('see lib/app.dart here')));
+    await tester.pumpAndSettle();
+    expect(find.textContaining('lib/app.dart'), findsOneWidget);
+    expect(tester.takeException(), isNull);
+  });
+
+  testWidgets('a backticked non-path code span stays verbatim (not linkified)', (tester) async {
+    await tester.pumpWidget(harness(f, md('run `flutter test` now')));
+    await tester.pumpAndSettle();
+
+    // A linkified ref renders as its own tappable Text; an inert code span is a
+    // styled run inside the paragraph, so it is not a standalone Text widget.
+    expect(find.text('flutter test'), findsNothing);
+    expect(tester.takeException(), isNull);
+  });
+}