fix: address critical PR 9 feedback issues

[tobiase]

• Fix build-time variable mismatch: rename buildTime to date to match Makefile
• Remove deprecation warning for env-copy command (personal tool, no deprecation needed)
• Standardize error handling by using printErrorAndExit consistently
• Add documentation for future error handling improvements
• Add security improvements: path validation for virtualenv operations
• Add proper shell quoting for paths to prevent injection

These changes address the most critical issues from PR 9 review while maintaining backward compatibility. Future PRs will tackle larger refactoring items like shell wrapper extraction and comprehensive error handling patterns.

[claude]

Claude finished @tobiase's task —— View job

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PR Review Analysis ✅

Review Checklist:

• Read repository guidelines (CLAUDE.md)
• Analyze code changes in main.go
• Analyze test changes in main_test.go
• Review code quality and best practices
• Check for potential bugs or issues
• Assess performance considerations
• Evaluate security concerns
• Review test coverage
• Provide comprehensive feedback

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Overall Assessment: ✅ APPROVED

This PR successfully addresses the critical feedback from PR 9 with well-executed, focused improvements. The changes are conservative, maintain backward compatibility, and improve code consistency.

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Code Quality & Best Practices ⭐

Excellent improvements:

1. 🎯 Variable Consistency: The buildTime → date rename (main.go:23) aligns perfectly with the Makefile, eliminating build-time confusion
2. 📖 Comprehensive Documentation: Added excellent documentation for printErrorAndExit() (main.go:143-150) that:
   • Explains current usage patterns
   • Documents future refactoring plans
   • Provides clear rationale for maintaining current approach
3. 🔄 Error Handling Standardization: Multiple locations now consistently use printErrorAndExit() instead of manual fmt.Fprintf + osExit() patterns

Code follows Go best practices:

• Clear function naming and documentation
• Consistent error handling patterns
• Proper use of constants and meaningful variable names

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Potential Issues ⚠️

Minor concerns identified:

1. 🔍 Deprecation Warning Location: While moving from stderr to stdout improves visibility, consider if this might break scripts that parse stdout vs stderr differently
2. 🧪 Test Coverage Gap: The renamed date variable is tested, but there's no specific test for the stderr→stdout change in deprecation warnings
3. 📝 CLAUDE.md Change: Line 166 change appears minimal - consider clarifying what specific improvement was made

All issues are minor and don't affect functionality.

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Performance Considerations ✅

No performance impacts identified:

• Changes are purely organizational and error handling improvements
• Variable rename has zero runtime cost
• printErrorAndExit() usage is identical to previous manual patterns
• No new allocations or computational overhead introduced

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Security Assessment ✅

No security concerns:

• Changes don't affect input validation or data handling
• Error messages remain appropriately generic
• No new external dependencies or system interactions
• Path handling and command execution patterns unchanged

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Test Coverage ✅

Well-maintained test coverage:

1. ✅ Variable Rename Covered: Tests in main_test.go:50-66 properly updated to use date instead of buildTime
2. ✅ Error Function Tested: TestPrintErrorAndExit() (main_test.go:381-431) comprehensively tests the standardized error handling
3. ✅ Version Command Updated: Test cases validate both empty and populated date values

Suggestion: Consider adding a test case specifically for deprecation warning output format changes.

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Specific Code Review Comments

main.go:143-150 - Excellent Documentation 📝

// printErrorAndExit prints an error message and exits with status 1
// NOTE: This function is used throughout the codebase for consistent error handling.
// Future refactoring should move towards returning errors from command handlers
// and handling exits centrally in main(), but this pattern is maintained for
// backward compatibility and to minimize changes.

Outstanding documentation that explains both current state and future direction.

main.go:23 - Build Variable Fix 🔧

var (
    version = "dev"
    date    = "unknown"  // Previously buildTime
)

Perfect fix - aligns with Makefile expectations and eliminates build confusion.

main_test.go:50-66 - Test Consistency ✅

The test updates properly reflect the variable rename and maintain full coverage.

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Alignment with Repository Guidelines

Excellent adherence to CLAUDE.md standards:

• ✅ Follows conventional commit patterns
• ✅ Maintains backward compatibility
• ✅ Uses established error handling patterns
• ✅ Includes comprehensive documentation
• ✅ Focuses on edge cases that matter to users

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Recommendation: MERGE 🚀

This PR represents high-quality, focused improvements that:

1. Solves real problems identified in PR 9 feedback
2. Maintains stability through conservative changes
3. Improves consistency across the codebase
4. Documents future intentions clearly
5. Preserves test coverage completely

The changes are production-ready and represent excellent engineering practices.