test: Add edge case tests for Hugo/Presidium generation

[richardwooding]

Summary

Add comprehensive edge case testing for Hugo site generation with Presidium layouts.

Context

Code review of PR #45 identified gaps in test coverage for edge cases and error scenarios.

Test Coverage Needed

1. Special Characters in enterprise_key

• Test server names with spaces (e.g., "My MCP Server")
• Test server names with special characters (e.g., "server@2.0", "test-server_v1")
• Test server names with unicode characters
• Verify Hugo YAML remains valid with these characters

2. Presidium Frontmatter Validation

• Test with missing required frontmatter fields (author, title)
• Test with invalid author format (non-email)
• Test with strict validation enabled/disabled
• Verify error messages are helpful

3. Module Download Failures

• Test behavior when Presidium modules are unavailable
• Test offline mode scenarios
• Test with invalid module paths
• Verify error handling provides actionable guidance

4. Menu Generation Edge Cases

• Test menu identifier generation with special characters
• Test with very long section names
• Test with duplicate section names
• Verify menu structure remains valid

Implementation Notes

• Use table-driven tests for multiple scenarios
• Mock network failures for module download tests
• Validate generated YAML syntax
• Ensure error messages guide users to solutions

References

• PR feat: switch from Hextra to Presidium layouts #45: Switch from Hextra to Presidium layouts
• Code review: feat: switch from Hextra to Presidium layouts #45 (comment)