Fix type_union_implicit rule for Draft 0, 1, and 2

[staging-devin-ai-integration]

Fix type_union_implicit rule for Draft 0, 1, and 2

Summary

Fixed a bug in the type_union_implicit canonicalizer rule where incorrect vocabulary URIs were being checked for JSON Schema Draft 0, 1, and 2. The rule was checking for hyper-schema# URIs instead of schema# URIs, which caused it to not detect when enum was present, incorrectly adding a type array alongside enum.

The root cause was an inconsistency within the rule itself - lines 21-30 correctly check for schema# URIs, but lines 101-117 were checking hyper-schema# URIs for the same drafts.

Review & Testing Checklist for Human

• Verify vocabulary URIs: Confirm that Draft 0, 1, and 2 should use schema# rather than hyper-schema# as the vocabulary identifier. This is consistent with Draft 3's check on line 96-98 which uses schema#.
• Check for regressions: Consider if any existing schemas using Draft 0, 1, or 2 might be affected by this behavioral change. Schemas with enum will no longer get the implicit type array added.
• Run the full test suite: Ensure all 650 tests in core.alterschema pass with no regressions.

Recommended test plan: Run make from the repository root to verify all tests pass and no formatting changes remain.

Notes

• Link to Devin run: https://staging.itsdev.in/sessions/d958f1b5dd374533885c2e0f6bc172fe
• Requested by: unknown ()

[staging-devin-ai-integration]

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