fix: line-count score configured null-language extensions instead of skipping them

[MkDev11]

Summary

Extensions configured in programming_languages.json with no language field receive score=0.0 with scoring_method='skipped-unsupported'. The scorer only routed a file to line-count scoring when its extension appeared in the NON_CODE_EXTENSIONS constant — it never consulted the JSON config. The 11 affected extensions are: env, gitattributes, gitignore, gql, graphql, ipynb, move, nim, pde, puml, tex.

Root cause: calculate_token_score_from_file_changes gated line-count scoring on ext in NON_CODE_EXTENSIONS. A configured null-language extension not in that list fell through to skipped-unsupported. Adding a weight to the JSON had no effect unless NON_CODE_EXTENSIONS was also updated — a silent maintenance trap.

Fix:

• Add TokenConfig.is_line_count_extension() — returns True when the extension is in NON_CODE_EXTENSIONS or is configured in programming_languages.json with language=None.
• Replace the ext in NON_CODE_EXTENSIONS gate with weights.is_line_count_extension(ext).
• Remove the now-unused NON_CODE_EXTENSIONS import from tree_sitter_scoring.py.

This is the null-language complement of #986, which fixed extensionless configured files that do have a tree-sitter language.

Related Issues

Closes #1274

Type of Change

• Bug fix

Testing

• Tests added/updated

TestNullLanguageLineCountScoring in tests/validator/test_token_scoring_integration.py:

• test_graphql_scores_line_count — primary reproduction case; asserts scoring_method='line-count' and score > 0
• test_gitignore_scores_line_count — dotfile extension path
• test_unknown_extension_stays_skipped_unsupported — negative control; confirms fix is bounded to configured extensions
• test_graphql_score_uses_configured_weight — pins exact value: graphql weight 1.0 × 1 line = 1.0
• test_all_configured_null_language_extensions_are_line_count_reachable — config-coverage guard; iterates every null-language entry in the JSON and fails if any future addition silently produces skipped-unsupported

Checklist

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