fix: coverage timeout

[wasabeef]

Summary

Fixed test coverage timeout issues in CI workflow.

Changes

• Added single-threaded test execution to prevent race conditions
• Increased coverage timeout configuration
• Fixed directory restoration fallback for CI environments

Results

• Coverage analysis now completes successfully without timeouts
• Tests run reliably in GitHub Actions CI environment

[github-actions]

📊 CI Results

✅ All Checks Passed

📋 Coverage & Testing

• Coverage: 27.7%
• Total Tests: 175
• Security Tests: 26
• Worktree Tests: 27
• Git Operations: 23

🎯 Quality Metrics

❌ Coverage: 27.7%
✅ Linting: All clippy warnings resolved
✅ Formatting: Code properly formatted
✅ Security: Comprehensive protection validated

🚀 Build Status

• Ubuntu: ✅ Passed
• macOS: ✅ Passed
• Artifacts: ✅ Generated

📦 Test Suite Optimization

• Test Files: 42 total (28 unified)
• Structure: Consolidated and comprehensive test coverage
• Efficiency: 60% of files are unified tests