fix: small reworks on git log sidebar

tests/renderer/components/GitSidebar.styles.test.ts

@@ -0,0 +1,22 @@
+import { describe, expect, it } from 'vitest';
+import * as fs from 'node:fs';
+import * as path from 'node:path';
+
+describe('GitSidebar styles', () => {
+  const cssPath = path.resolve(
+    __dirname,
+    '../../../src/renderer/components/GitSidebar/GitSidebar.css'
+  );
+
+  it('limits version history section to 50% of available sidebar room', () => {
+    const css = fs.readFileSync(cssPath, 'utf8');
+
+    expect(css).toMatch(/\.git-sidebar-history\s*\{[^}]*flex:\s*0\s+0\s+50%;[^}]*max-height:\s*50%;[^}]*\}/s);
+  });
+
+  it('keeps commit list scrollable within the bounded history section', () => {
+    const css = fs.readFileSync(cssPath, 'utf8');
+
+    expect(css).toMatch(/\.git-sidebar-history-list\s*\{[^}]*overflow:\s*auto;[^}]*\}/s);
+  });
+});