test: Add context-detector edge case tests

- Test for settings.json without permissions field
- Test for undefined cwd
- Test for cwd without context files

Coverage: 93.92% (218 tests)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tui/src/lib/context-detector.test.ts

@@ -42,6 +42,34 @@ describe('detectContextFiles', () => {
     expect(result.projectSettings).toBe(true);
     expect(result.projectSettingsRules).toBe(3);
   });
+
+  it('handles settings.json without permissions field', () => {
+    const settingsPath = path.join(tmpDir, '.claude', 'settings.json');
+    fs.mkdirSync(path.dirname(settingsPath), { recursive: true });
+    fs.writeFileSync(settingsPath, JSON.stringify({ someOtherField: true }), 'utf-8');
+
+    const result = detectContextFiles(tmpDir);
+
+    expect(result.projectSettings).toBe(true);
+    expect(result.projectSettingsRules).toBe(0);
+  });
+
+  it('returns default values when cwd is undefined', () => {
+    const result = detectContextFiles(undefined);
+
+    expect(result.projectClaudeMd).toBe(false);
+    expect(result.projectClaudeMdPath).toBeNull();
+    expect(result.projectSettings).toBe(false);
+  });
+
+  it('returns default values when cwd has no context files', () => {
+    const result = detectContextFiles(tmpDir);
+
+    expect(result.projectClaudeMd).toBe(false);
+    expect(result.projectClaudeMdPath).toBeNull();
+    expect(result.projectSettings).toBe(false);
+    expect(result.projectSettingsRules).toBe(0);
+  });
 });
 
 describe('ContextDetector', () => {