refactor: remove unneeded sidecar refresh restart logic

Drop the refresh-time sidecar restart workaround and its helper/tests now that the verified fix is in the sidecar subprocess launcher itself. This keeps the runtime simpler and leaves only the changes required for correct Copilot version detection.

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

tests/main/sidecarRefresh.test.ts

@@ -1,31 +0,0 @@
-import { describe, expect, test } from 'bun:test';
-
-import {
-  shouldHandleSidecarExit,
-  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);
-  });
-});
-
-describe('shouldHandleSidecarExit', () => {
-  test('handles exit events from the currently active sidecar process', () => {
-    expect(shouldHandleSidecarExit(1234, 1234)).toBe(true);
-  });
-
-  test('ignores exit events from a stale sidecar process', () => {
-    expect(shouldHandleSidecarExit(1234, 5678)).toBe(false);
-  });
-
-  test('ignores exit events when either process id is missing', () => {
-    expect(shouldHandleSidecarExit(undefined, 5678)).toBe(false);
-    expect(shouldHandleSidecarExit(1234, undefined)).toBe(false);
-  });
-});