Add CI (build :core + :plugin, run parser tests on push)

[GabrielBBaldez]

The plugin has no CI — nothing builds or runs the parser tests on push.

The build is already CI-ready. In plugin/build.gradle.kts:

val localIde = providers.gradleProperty("localIdePath").orNull
if (localIde != null) local(localIde) else intellijIdeaCommunity("2024.3.5")

So when -PlocalIdePath is not passed (the CI case), Gradle downloads IntelliJ IDEA Community on its own. A workflow just runs the build without that property.

What to do

Add .github/workflows/ci.yml:

• actions/checkout@v4
• actions/setup-java@v4 with Temurin 21
• gradle/actions/setup-gradle@v4 (gives Gradle caching)
• run ./gradlew build — compiles :core + :plugin, runs the :core parser tests, and buildPlugin packages the zip. Do not pass -PlocalIdePath in CI.
• add ./gradlew verifyPlugin if you want the plugin-structure check too.

Cache the IntelliJ Platform download as well (the IDE artifact is ~1 GB); setup-gradle caches ~/.gradle, and the platform cache lives there too, so cold runs are slow but warm runs are fast.

Trigger on push (main) and pull_request.

How to verify

The first run is green and does the IDE download; a follow-up push reuses the cache. A red build should block the change.