give the status-bar context slot a flexible share

StatusbarHost laid every item at intrinsic width, so once the focused-pane
context line grew long (a model/mode/context/skills summary) the row's
content exceeded the bar width and overflowed instead of letting the slot
shrink. Add an opt-in flex factor to StatusItemContribution; the host wraps
flex>0 items in Flexible(loose) so they yield width when the bar is tight,
and the marquee then receives a bounded viewport and scrolls. Drops the
fixed maxWidth cap on the pane-context item.

T-160.

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

test/builtin/claude/pane_context_status_test.dart

@@ -1,16 +1,54 @@
-/// Tests for the focus-driven status-bar slot item (T-150): it renders
-/// the focused pane's status widget and clears when focus moves to a
-/// pane with no status.
+/// Tests for the focus-driven status-bar slot item (T-150 / T-160): it
+/// renders the focused pane's status widget and clears when focus moves
+/// to a pane with no status; at a constrained width the slot never
+/// overflows and ClideMarquee gets a bounded viewport.
 library;
 
 import 'package:clide/builtin/claude/src/pane_context_status.dart';
-import 'package:clide/kernel/src/panels/slot_id.dart';
+import 'package:clide/kernel/kernel.dart';
+import 'package:clide/widgets/widgets.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 import '../../helpers/kernel_fixture.dart';
 import '../../helpers/widget_harness.dart';
 
+/// Wraps [child] in a Row with Flexible(loose), mirroring the layout that
+/// StatusbarHost applies to left-side flex items (T-160), inside a
+/// [SizedBox] of the given [width].
+///
+/// Deliberately does NOT use the shared [harness] here: that one mounts an
+/// `Overlay(canSizeOverlay: true)` over a zero-size MediaQuery, which runs an
+/// intrinsic-sizing pass and hands children unbounded width — so a `Flexible`
+/// never bounds the marquee and this test could not observe the fix. We mount
+/// the minimum theme/kernel tree under a tight, [Align]ed [SizedBox] so the
+/// `Flexible` gets a real bounded width from the surrounding Row.
+Widget _narrowRow(KernelFixture f, double width, Widget child) => Directionality(
+      textDirection: TextDirection.ltr,
+      child: ClideKernel(
+        services: f.services,
+        child: ClideTheme(
+          controller: f.services.theme,
+          child: MediaQuery(
+            data: const MediaQueryData(),
+            child: Align(
+              alignment: Alignment.topLeft,
+              child: SizedBox(
+                width: width,
+                height: 24,
+                child: Row(
+                  children: [
+                    Flexible(flex: 1, fit: FlexFit.loose, child: child),
+                    const SizedBox(width: 20), // simulated right-side items
+                  ],
+                ),
+              ),
+            ),
+          ),
+        ),
+      ),
+    );
+
 void main() {
   late KernelFixture f;
   setUp(() async => f = await KernelFixture.create());
@@ -32,4 +70,53 @@ void main() {
     await tester.pump();
     expect(find.text('S'), findsNothing);
   });
+
+  // T-160: at a narrow bar width the slot must never overflow and
+  // ClideMarquee must receive a bounded (scrollable) viewport.
+  testWidgets('no RenderFlex overflow at narrow width — ClideMarquee is bounded', (tester) async {
+    // A long status line similar to what T-154 added:
+    // "opus 4.7 · default · 21k ctx · 10 skills" — roughly 280 px of text.
+    const longStatus = Text(
+      'opus 4.7 · default · 21k ctx · 10 skills',
+      textDirection: TextDirection.ltr,
+      softWrap: false,
+    );
+
+    // Pump at 200 px wide — narrower than the status content so the marquee
+    // must receive a bounded viewport < content width and start scrolling.
+    const barWidth = 200.0;
+    await tester.pumpWidget(_narrowRow(f, barWidth, const PaneContextStatusItem()));
+    await tester.pump(); // first frame — nothing focused yet
+
+    final focus = f.services.focus;
+    focus.setActive(slot: Slots.workspace, contributionId: 'pane.z');
+    focus.setStatusWidget('pane.z', longStatus);
+    await tester.pump(); // status widget appears
+    await tester.pump(); // ClideMarquee _measure post-frame callback
+
+    // 1. No overflow exception.
+    expect(tester.takeException(), isNull);
+
+    // 2. The ClideMarquee is in the tree.
+    expect(find.byType(ClideMarquee), findsOneWidget);
+
+    // 3. The ClideMarquee render box is bounded — its width must be less than
+    //    barWidth (the slot shrinks to fit, not past the container).
+    final marqueeSize = tester.getSize(find.byType(ClideMarquee));
+    expect(marqueeSize.width, lessThan(barWidth));
+    expect(marqueeSize.width, greaterThan(0));
+
+    // Dispose the ticker by tearing down the widget tree.
+    await tester.pumpWidget(const SizedBox());
+  });
+
+  testWidgets('no overflow when no status is active — slot is shrunk', (tester) async {
+    const barWidth = 200.0;
+    await tester.pumpWidget(_narrowRow(f, barWidth, const PaneContextStatusItem()));
+    await tester.pump();
+
+    // No focused pane → SizedBox.shrink path. No overflow, no marquee.
+    expect(tester.takeException(), isNull);
+    expect(find.byType(ClideMarquee), findsNothing);
+  });
 }