defect: security restrictions broke test infrastructure - systematic test failures

[krystophny]

SYSTEMATIC TEST INFRASTRUCTURE BREAKDOWN

The security 'fixes' in PR #517 broke the test infrastructure by disabling directory creation, causing multiple test failures masked as 'EXPECTED FAIL'.

Broken Test Infrastructure:

test_example_output_structure.f90 contains 6+ execute_command_line calls for directory creation:

• Lines 32-48: Windows and Unix directory creation commands
• ALL directory creation operations now FAIL due to security restrictions
• Test reports multiple 'EXPECTED FAIL' conditions hiding real failures

Test Failure Evidence:

EXPECTED FAIL: bar_chart_demo output directory missing - needs creation
EXPECTED FAIL: errorbar_demo output directory missing - needs creation  
EXPECTED FAIL: histogram_demo output directory missing - needs creation
EXPECTED FAIL: Cross-platform directory creation needs implementation

Root Cause:
Security PR claimed to eliminate execute_command_line but instead:

1. Left execute_command_line calls active in test code
2. Disabled functionality without providing alternatives
3. Masked test failures as 'expected' behavior

System Impact:

• Example generation infrastructure BROKEN
• Output directory creation FAILS
• Test suite gives FALSE PASSING results
• GitHub Pages documentation generation likely BROKEN
• Cross-platform compatibility DESTROYED

Steps to Reproduce:

fpm test --target test_example_output_structure
# Shows multiple 'EXPECTED FAIL' that are actually system failures

Expected: Secure directory creation alternatives implemented
Actual: Core functionality disabled, test infrastructure broken

Severity: HIGH - Test infrastructure systemic failure
Component: Test Infrastructure, Directory Operations

[krystophny]

DUPLICATE: Consolidating with #550 - same root cause of security restrictions breaking tests