feat: add optional Rich-powered terminal UI for parsed content

[GhostWr1t3r]

Description

Adds an optional Rich-powered terminal UI for parsed content, improving readability in CLI environments while maintaining backward compatibility.

Type of Change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

• Unit tests: Verified UI wrapper preserves original content

  def test_ui_does_not_alter_content():
      raw, _ = parser.parse("test.pdf")
      ui, _ = parser.parse("test.pdf", show_ui=True)
      assert raw == ui  # Content integrity check

• Performance benchmarks:

  Mode	Avg Time (10 runs)
  Default	3.70s
  UI Enabled	4.71s ±1.01s

• Manual verification:
  Tested with PDF/DOCX/HTML inputs

Screenshots

Before:

After:

Checklist

• Code follows project style guidelines
• Self-review performed
• Comments added for complex logic
• Documentation updated (README.md)
• No new warnings generated
• Tests added (content integrity + performance)
• All tests pass locally

Additional Notes

• Zero dependency impact: Uses rich
• Opt-in design: No behavior changes unless show_ui=True
• Extensible: Theme configurations can be added later