fix: restart idle sidecar on capability refresh

Force-refreshing sidecar capabilities now disposes the idle sidecar process before re-querying capabilities, so Kopaya can pick up backend sidecar changes and refreshed Copilot connection state without a full app restart.

Add a small helper and regression tests for the refresh decision.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

tests/main/sidecarRefresh.test.ts

@@ -0,0 +1,13 @@
+import { describe, expect, test } from 'bun:test';
+
+import { shouldRestartSidecarOnCapabilityRefresh } from '@main/sidecar/sidecarRefresh';
+
+describe('shouldRestartSidecarOnCapabilityRefresh', () => {
+  test('restarts the sidecar when no run-turn is active', () => {
+    expect(shouldRestartSidecarOnCapabilityRefresh(false)).toBe(true);
+  });
+
+  test('keeps the existing sidecar when a run-turn is active', () => {
+    expect(shouldRestartSidecarOnCapabilityRefresh(true)).toBe(false);
+  });
+});