OpenAPI 3.2: Create sub-issues for all 18 adoption opportunities

[Copilot]

Summary

Breaks down OpenAPI 3.2 — Opportunities for Counterfact (#1673) into 18 actionable sub-issue proposals covering every identified opportunity, from the trivial (server name field) to the substantial (SSE streaming).

Each proposal file in .github/issue-proposals/ includes current state, concrete file-level change targets, and observable acceptance criteria. On merge, CI converts them to real GitHub issues linked as sub-issues of #1673.

Original Prompt

OpenAPI 3.2 was released in early 2025. This issue identifies changes in the specification and maps each one to a concrete opportunity for Counterfact to adopt it so that Counterfact can be listed as an OpenAPI 3.2 early adopter on openapi.tools. Break this issue down into subtasks.

Manual acceptance tests

• All 18 proposal files are present under .github/issue-proposals/openapi-32-*.md
• Each proposal has valid YAML front matter with parentIssue: 1673, a non-empty title, and at least one label
• Each proposal body contains a non-empty description and a checklist of acceptance criteria
• The CI create-issues workflow processes all 18 files without validation errors on merge
• All created issues appear as sub-issues of OpenAPI 3.2 — Opportunities for Counterfact #1673 after merge

Tasks

• Created 18 issue proposal files under .github/issue-proposals/:

Proposal	Feature
openapi-32-query-http-method.md	1a. Native QUERY HTTP method
openapi-32-additional-operations.md	1b. additionalOperations for arbitrary methods
openapi-32-streaming-sse-itemschema.md	2. Streaming / SSE via itemSchema
openapi-32-querystring-parameter.md	3. querystring parameter location
openapi-32-datavalue-serializedvalue-examples.md	4. dataValue/serializedValue examples
openapi-32-optional-discriminator-propertyname.md	5a. Optional discriminator propertyName
openapi-32-discriminator-default-mapping.md	5b. Discriminator defaultMapping
openapi-32-tag-enhancements.md	6. Tag summary/parent/kind
openapi-32-optional-response-description.md	7a. Optional response description
openapi-32-response-summary-ui.md	7b. Response summary in UI
openapi-32-oauth2-device-authorization.md	8a. OAuth2 Device Authorization flow
openapi-32-oauth2-metadata-url.md	8b. oauth2MetadataUrl display
openapi-32-deprecated-security-scheme.md	8c. @deprecated for deprecated security schemes
openapi-32-self-document-identity.md	9. $self document identity
openapi-32-components-mediatypes.md	10. components/mediaTypes $ref resolution
openapi-32-xml-nodetype.md	11. XML nodeType field
openapi-32-server-name-field.md	12. Server Object name field
openapi-32-json-schema-alignment.md	13. JSON Schema draft-bhutton-01 alignment