Fix frontend 0.1 schema for v0.2.1

[TonisOrmisson]

What changed

• corrects malformed empty JSON object keys to Draft 2020-12 $defs and $ref keywords in the published SPSS Syntax Frontend 0.1 schema
• documents the narrow policy for backporting schema defects without changing normative meaning
• records v0.2.1 as an unpublished patch target

Scope

This maintenance branch starts exactly at the published v0.2.0 commit 79339ec3d8f8aa81789b7e85f6b8afa6f1374e50. It contains no v0.3.0 release-candidate work, executable validator, parser, compiler, adapter logic, or package tooling.

The correction restores the typed-value constraint already stated by the contract; it does not broaden the accepted contract or add new normative behavior.

Validation

• python3 tools/validate_repository.py
• git diff --check release/0.2...HEAD
• independent strong review: CLEAN

Release status

This PR prepares, but does not publish, v0.2.1. The final dated changelog commit, exact-head CI/review, protected or signed tag, and verified GitHub Release remain separate release steps.

[TonisOrmisson]

@codex review

Please review exact maintenance head e599c984dbfe8020df6e3a5ea860645a6eb4c9cd against release/0.2 / published v0.2.0. Confirm that the JSON Schema correction only restores the existing typed-value contract, that no v0.3 or executable tooling content is present, and that the release metadata is appropriate for an unpublished v0.2.1 patch candidate.

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Hooray!

Reviewed commit: e599c984db

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[TonisOrmisson]

@codex review

Please review final exact head 3108eae71fa02d66a47e924adac649a3945ad017. The only change since the prior clean review is finalizing the changelog heading/date for v0.2.1; both exact-head push and PR CI runs are green. Please confirm the maintenance patch remains isolated from v0.3 and release-ready.

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. What shall we delve into next?

Reviewed commit: 3108eae71f

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".