Implement directory rendering with relative path preservation

[Matographo]

Summary

Render full directory trees into a target directory while keeping relative input structure intact.

Why

Directory rendering is one of the product’s core operating modes and must integrate with file-scoped rules correctly.

Acceptance Criteria

• Directory rendering preserves structure
• File-scoped rule resolution works within directory renders
• Errors report the affected file path clearly

Dependencies

• Depends on Implement output routing for stdout, output file, and output directory #5
• Depends on Implement deterministic rule precedence resolution #13
• Depends on Implement the core renderer for strings and single files #22