Add script to extract required phrases from rule files

[Kaushik-Kumar-CEG]

references #5077

Adds a script to extract required phrase annotations ({{ }} markers) from .RULE files and output them as JSONL for NER model training

The script handles:

• marker extraction with correct character positions
• phrase normalization (HTML entities, xml tags, backticks, whitespace)
• unicode and line ending normalization
• position validation

more features (BIOES labels, train/val/test split, plain text field) coming in follow-up commits

disclosure : used Claude to help review and clean up few bugs in script

Tasks

• Reviewed contribution guidelines
• PR is descriptively titled and links the original issue above
• Tests pass
• Commits are in uniquely-named feature branch and has no merge conflicts
• Updated documentation pages (if applicable)
• Updated CHANGELOG.rst (if applicable)

[Kaushik-Kumar-CEG]

@AyanSinhaMahapatra ready for review when you get a chance. ill make the follow up changes to script as well