Document shared infrastructure usage

Co-authored-by: Codex <codex@openai.com>

Author: handrews

CONTRIBUTING.md

@@ -25,6 +25,23 @@ When you engage with this project, please:
 We actively close interactions that don't meet these expectations, so please don't be offended as we protect the time and energy of our volunteers.
 If you do think that something was closed in error, you are welcome to reach out to us to follow up.
 
+## Shared infrastructure
+
+This repository uses the shared OpenAPI Initiative infrastructure package
+[`@oai/build-infra`](https://github.com/OAI/build-infra) for Markdown
+validation, HTML builds, schema publication, schema tests, and release helper
+commands. The npm scripts in this repository are intentionally thin wrappers
+around that package.
+
+The shared infrastructure docs explain how the tooling works and how to maintain
+it:
+
+- [build-infra README](https://github.com/OAI/build-infra/blob/main/README.md)
+- [build-infra CONTRIBUTING](https://github.com/OAI/build-infra/blob/main/CONTRIBUTING.md)
+
+Most contributors only need the commands shown below. Maintainers changing the
+tooling itself should read the build-infra docs first.
+
 
 ### Active branches
 
@@ -233,6 +250,11 @@ The steps for creating a `vX.Y.Z-rel` branch are:
 
 The HTML renderings of the specification versions are generated from the `versions` directory on `main` by manually triggering the [`respec` workflow](https://github.com/OAI/OpenAPI-Specification/blob/main/.github/workflows/respec.yaml), which generates a pull request for publishing the HTML renderings to the [spec site](https://spec.openapis.org).
 
+The release commands are implemented in
+[`OAI/build-infra`](https://github.com/OAI/build-infra). If a command behaves
+unexpectedly, check this repository's `spec.config.json` first, then see the
+[build-infra release documentation](https://github.com/OAI/build-infra/blob/main/README.md#release-process-summary).
+
 #### Start Next Patch Version
 
 Once the released specification version is [synced](#branch-sync-automation) back to the `vX.Y-dev` branch, the next patch version X.Y.(Z+1) can be started:

README.md

@@ -33,6 +33,13 @@ Looking to see how you can create your own OpenAPI definition, present it, or ot
 The current process for developing the OpenAPI Specification is described in
 the [Contributing Guidelines](CONTRIBUTING.md).
 
+Build, test, schema publication, and release command infrastructure is shared
+with other OpenAPI Initiative specification repositories through
+[OAI/build-infra](https://github.com/OAI/build-infra). See that repository's
+[README](https://github.com/OAI/build-infra/blob/main/README.md) and
+[CONTRIBUTING guide](https://github.com/OAI/build-infra/blob/main/CONTRIBUTING.md)
+for details on the shared tooling.
+
 Developing the next version of the OpenAPI Specification is guided by the [Technical Steering Committee (TSC)](MAINTAINERS.md). This group of committers bring their API expertise, incorporate feedback from the community, and expand the group of committers as appropriate. All development activity on the future specification will be performed as features and merged into this branch. Upon release of the future specification, this branch will be merged to `main`.
 
 The TSC holds weekly web conferences to review open pull requests and discuss open issues related to the evolving OpenAPI Specification. Participation in weekly calls and scheduled working sessions is open to the community. You can view the entire OpenAPI [technical meeting calendar](https://calendar.google.com/calendar/u/0/embed?src=c_fue82vsncog6ahhjvuokjo8qsk@group.calendar.google.com) online.
@@ -51,4 +58,3 @@ Not all feedback can be accommodated, and there may be solid arguments for or ag
 
 See: [License (Apache-2.0)](https://github.com/OAI/OpenAPI-Specification/blob/main/LICENSE)
 
-