Resolve the Gradle plugin from the Code Genome Project

[timtebeek]

• Follow-up to Maven Central -> Code Genome Project #522 / Resolve rewrite artifacts from the Code Genome Project repository #528 / Document settings.xml repositories for Maven command line usage #531, covering Gradle. Companion to Point remaining Maven instructions at the Code Genome Project #535 (Maven).

This is a live breakage, not just doc residue

Following getting-started.md exactly does not work today. Verified with Gradle 8.14.3:

plugins { id 'org.openrewrite.rewrite' version '7.41.0' }
repositories { mavenCentral() /* + CGP, as the docs currently show */ }

> Could not resolve org.openrewrite:plugin:7.41.0
   > Could not parse POM .../plugin-7.41.0.pom
      > Could not resolve org.openrewrite:rewrite-bom:8.91.0

The marker and the plugin jar are still on the Portal, but org.openrewrite:plugin's runtimeElements declares org.openrewrite:rewrite-bom:8.91.0, and that is 404 on both the Portal's m2 mirror and Maven Central (last version on either is 8.90.4). It resolves on the buildscript classpath, so the project-level repositories block the earlier PRs added does not help.

Confirmed three ways:

• 7.39.0 (bom 8.89.0, still on Central) → rewriteDiscover succeeds on Portal + mavenCentral() alone.
• Serving rewrite-bom:8.91.0 from a repository in pluginManagement.repositories gets past the classpath; the only remaining failure is the runtime core-lib resolution that project-level CGP already covers.
• The init-script path fails identically.

So Gradle needs the Code Genome Project in two places, and this PR adds the missing one everywhere.

What changed

• src/components/RunRecipe/index.tsx — one edit covering every generated recipe page. Adds a settings.gradle pluginManagement step and a gradle.properties step to the Gradle tab, and moves the init scripts' classpath resolution from plugins.gradle.org/m2 to the Code Genome Project.
• running-recipes/getting-started.md, reference/gradle-plugin-configuration.md — pluginManagement alongside the existing project repositories, with an explanation of why both are needed.
• running-rewrite-on-a-gradle-project-without-modifying-the-build.md — Code Genome Project inside initscript { repositories }, Groovy and Kotlin.
• running-text-based-recipes.md, running-rewrite-on-an-infrastructure-as-code-project.md, authoring-recipes/data-tables.md, popular-recipe-guides/automatically-fix-checkstyle-violations.md, authoring-declarative-yaml-recipes.md — same two-place fix.
• authoring-recipes/recipe-development-environment.md, recipe-testing.md, refaster-recipes.md, writing-kotlin-recipes.md — recipe-module builds had no repositories block at all for the rewrite modules they compile against.
• reference/latest-versions-of-every-openrewrite-module.md — drops the claim that the Gradle plugin is published to the Plugin Portal.
• reference/snapshot-instructions.md — Gradle snapshots now come from the Code Genome Project.
• reference/building-openrewrite-from-source.md — the isolated-environment allowlist needed a Code Genome Project mirror entry.

Credentials

Gradle snippets now read codeGenomeUsername / codeGenomeToken via providers.gradleProperty(...) instead of inlining USERNAME / TOKEN, with guidance to keep them in ~/.gradle/gradle.properties (or ORG_GRADLE_PROJECT_* env vars in CI).

Init scripts are the exception: they run before any project is configured and cannot read gradle.properties, so those use CODE_GENOME_USERNAME / CODE_GENOME_TOKEN environment variables. Called out inline where it appears.

Assumptions to confirm

1. Plugin markers on the Code Genome Project. plugins { id("org.openrewrite.rewrite") version "…" } resolving from a plain Maven repository requires the org.openrewrite.rewrite:org.openrewrite.rewrite.gradle.plugin marker POM to be published there alongside org.openrewrite:plugin. I could not verify this — every path under /maven returns 401 whether or not it exists. If markers are not published, these snippets need a resolutionStrategy or a buildscript block instead.
2. Snapshots live under the same https://artifacts.codegenomeproject.org/maven URL (there is no separate /maven-snapshots or /snapshots endpoint — both 404).
3. Is rewrite-bom on the plugin's runtimeElements intended? If it gets shaded or dropped upstream, the pluginManagement requirement goes away for the plugin classpath, though it would still be needed once the plugin itself leaves the Portal.

Verification

yarn build with CI_STRICT_LINKS=1 passes locally, and the rendered recipe pages were spot-checked. All Gradle snippets in this PR were syntax-checked by running them through Gradle 8.14.3.

[mike-solomon]

Thanks for the work on this! One minor comment below.

I do recognize that there is a lot of duplicated information throughout this - in the future we may want to investigate a partial that can be plugged in to various pages - but I don't think it's necessary right now.