Validate Mintlify slugs across OpenAPI specs

[danielporterda]

Summary

Follow-up to #780. Extend the Mintlify-safe OpenAPI summary handling and validation across every published OpenAPI spec under docs-main/openapi, not just the Splice Token Metadata regression case.

Changes

• Teach the JSON Ledger API OpenAPI generator to normalize existing path-only summaries, not only missing summaries, so pulled OpenAPI specs with GET /path/{param} summaries are rewritten to GET /path/:param before Mintlify sees them.
• Add scripts/validate_mintlify_openapi_slugs.py and npm run validate:mintlify-openapi-slugs to scan all published OpenAPI specs for Mintlify-style operation route collisions.
• Update JSON API OpenAPI tests to cover path-only summary normalization while preserving descriptive summaries.

Regeneration

Ran both OpenAPI generation paths:

• direnv exec . npm run generate:json-api-reference
• direnv exec . npm run generate:splice-mintlify-openapi

No additional generated output changes were produced on top of current main / #780.

Validation

• direnv exec . npm run validate:mintlify-openapi-slugs (12 specs)
• direnv exec . python3 -m pytest tests/test_json_api_openapi.py tests/test_splice_mintlify_openapi.py
• direnv exec . npm run validate:splice-mintlify-openapi-nav
• direnv exec . python3 -m py_compile scripts/generate_json_api_reference.py scripts/generate_splice_mintlify_openapi.py scripts/validate_splice_mintlify_openapi_nav.py scripts/validate_mintlify_openapi_slugs.py
• direnv exec . git diff --check