Oas 3.2 support (fix OAS 3.2 schema validation and align with 3.0/3.1)

[AnastasiiaSvietlova]

Fixes #2910.

Checklist

• Tests added / updated
• Docs added / updated

Does this PR introduce a breaking change?

• Yes
• No

Additional context

Builds on @mkistler's #2917, adding fixes found during review and finishing the test coverage. Co-authored with @mkistler to keep their original contribution intact and attributed.

This follow-up work (review, root-cause analysis, and fixes) was done with the help of AI (Claude Code), same as the original PR.

What #2917 added

• oas3_2 format detection (packages/formats/src/openapi.ts)
• The official OpenAPI 3.2 JSON Schema bundle (schema, dialect, meta), wired into document validation
• Extended oas3_1-only rules (oas3_1-servers-in-webhook, oas3_1-callbacks-in-webhook, the ArrayProperties alias) to also cover oas3_2
• A new rule, oas3_2-no-deprecated-xml-attribute

What this PR adds on top

⚠️ Main fix: oas3-schema rejected virtually every real OAS 3.2 document
This is the important one — please read this section.

The vendored 3.2 schema uses $dynamicRef: "#meta" (5 places, e.g. media-type.schema) to point at a $dynamicAnchor nested inside $defs.schema. AJV does not correctly resolve a $dynamicAnchor declared anywhere other than a schema resource's root — see ajv-validator/ajv#1745 and #1573 (a near-identical report against the OAS 3.1 schema, where other validators like Hyperjump/jschon handle the same schema correctly). Instead of resolving to the intended anchor, AJV fell back to re-validating the schema value against the document's own root rules, rejecting any real type/properties as unrecognized fields. In practice: any 3.2 document with a schema in a request/response body, parameter, or header failed oas3-schema — i.e. almost any real API.

Fix: replaced the 5 $dynamicRef: "#meta" occurrences in v3.2/index.json with a static $ref to https://spec.openapis.org/oas/3.2/dialect/2025-09-17 — the same workaround the AJV issue reporter used, and the same pattern already used successfully by v3.1/index.json. Verified both directions: previously-failing valid documents now pass, and invalid documents (bad type values) are still correctly rejected.

Smaller fixes (see commit/diff for detail)

• Error-message parity: added the same custom errorMessage annotations v3.1/index.json has, so OAS 3.2 gets equally readable errors instead of raw AJV dumps.
• Unrelated terser bump reverted: package.json bumped it but yarn.lock wasn't updated, which would fail CI's immutable install. No connection to this PR's purpose, no security reason found.
• Deduped oasSchema.ts: the new oas3_2 branch was a verbatim copy of oas3_1's.
• Documented a scope decision: oas3_2-no-deprecated-xml-attribute intentionally only flags xml.attribute: true, not false (no actionable migration for false).
• Test coverage: OAS 3.2 cases added to oas3-schema.test.ts, plus new test-harness/scenarios/oas3.2/ CLI scenarios, mirroring existing 3.0/3.1 coverage.

The contributor's own AI-assisted coverage checklist identified some OpenAPI 3.2 features that aren't fully covered yet (e.g. xml.wrapped, the new query HTTP method in operation-rules, $self ref resolution). Left out of scope here to keep this PR focused; worth tracking as separate follow-up issues.