feat: add --output-dir and --output-file CLI options

[okwn]

Summary

Adds --output-dir and --output-file CLI options to run_pageindex.py, allowing users to specify custom output paths for scripted/automated usage.

Fixes issue #268.

Changes

• Added --output-dir argument (default: ./results) to specify output directory
• Added --output-file argument to specify exact output file path (overrides default naming)
• Both options work for PDF and markdown processing

Testing

• Verified --help shows new options
• Tested with sample markdown file using custom output path

Example Usage

# Custom output directory
python run_pageindex.py --pdf_path doc.pdf --output-dir /tmp/pi_out

# Custom output file
python run_pageindex.py --md_path doc.md --output-file /tmp/my_result.json