Clarify GTS annotation scope and expand OP#12/OP#13 compatibility coverage

[aviator5]

• Clarifies that x-gts-* annotation keywords have GTS semantics only in Type Schema documents; same-named fields in instances are ordinary data unless constrained by the instance schema.
• Adds conformance coverage for OP#12/OP#13 edge cases around closed descendant schemas, orphaned ancestor properties/traits, abstract trait-schema compatibility, and valid trait-schema narrowing.

Summary by CodeRabbit

• Documentation

  • Clarified how certain GTS keywords are interpreted in instance documents.
  • Updated wording so these fields are treated as normal data unless a schema explicitly constrains them.

• Tests

  • Added coverage for nested closure and ancestor-property validation rules.
  • Expanded trait-schema validation tests for abstract and non-abstract compatibility cases.
  • Removed tests that expected instance documents to be rejected solely for containing GTS keyword names.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: ac54d9ad-2744-4bfc-9deb-0a5cddd9cdf2

📥 Commits

Reviewing files that changed from the base of the PR and between 148e146 and a42b477.

📒 Files selected for processing (4)

• README.md
• tests/test_op12_type_derivation_validation.py
• tests/test_op13_schema_traits_validation.py
• tests/test_refimpl_x_gts_final_abstract.py

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📝 Walkthrough

Walkthrough

README wording now treats x-gts-traits-schema, x-gts-traits, x-gts-final, and x-gts-abstract as meaningful only in JSON Schema documents. The tests add closed-descendant and trait-schema compatibility cases, and remove instance-body rejection coverage for x-gts-final and x-gts-abstract.

Changes

GTS keyword semantics

Layer / File(s)	Summary
Keyword placement semantics README.md, tests/test_refimpl_x_gts_final_abstract.py	Updates the spec wording for x-gts-* keywords in instance documents and removes the x-gts-final / x-gts-abstract instance-body rejection tests.
Closed descendant validation tests/test_op12_type_derivation_validation.py, tests/test_op13_schema_traits_validation.py	Adds the OP 12 nested closed-descendant failure case, imports register_instance, and expands OP 13 with abstract trait-schema compatibility and orphaning cases under allOf, plus removal of the instance-document trait keyword rejection tests.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• GlobalTypeSystem/gts-spec#61: Introduced the OP 13 trait keyword semantics and the x-gts-traits-schema / x-gts-traits README and test coverage that this PR updates.
• GlobalTypeSystem/gts-spec#67: Added the x-gts-final / x-gts-abstract modifier support whose instance-body rejection tests are removed here.
• GlobalTypeSystem/gts-spec#77: Defines the ADR-focused trait-schema compatibility and orphaning rules that the new OP 13 tests exercise.

Suggested reviewers

• Artifizer

Poem

🐇 I nibbled the schema moonbeams bright,
and tucked old keyword rules out of sight.
Closed burrows now ask fields to stay aligned,
while instance leaves are just data defined.
Hop-hop—clean tests in the cool night!

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the README scope clarification and the added OP#12/OP#13 compatibility tests.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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