fix(scoring): add ERB file scoring support

[eureka928]

Summary

• Add .erb (Embedded Ruby) extension to programming_languages.json with weight 0.8
• Add erb to NON_CODE_EXTENSIONS in constants.py for line-count scoring

Related Issues

ERB files (.erb, .html.erb) used in Rails projects were completely unscored — they had no entry in programming_languages.json and no tree-sitter parser exists in the language pack. This meant any PR modifying only ERB files would get 0 token score.

Since no tree-sitter ERB parser is available, line-count scoring is the only viable method. Weight of 0.8 reflects ERB being a mix of HTML (0.75) and Ruby (1.75) template code.

Scoring behavior:

• ERB changes contribute to the contribution bonus only (not pr.token_score)
• ERB-only PRs get a small base score (max ~3.60 per file at 300-line cap)
• Mixed PRs (.rb + .erb) get ERB as a small bonus on top of Ruby AST scoring
• ERB changes do not count toward tier token score thresholds

Type of Change

• Bug fix
• New feature
• Refactor
• Documentation
• Other (describe below)

Testing

• Tests added/updated
• Manually tested
• All 199 existing tests pass

Checklist

• Code follows project style guidelines
• Self-review completed
• Changes are documented (if applicable)