Baseline: Ludic compiler + toolchain, Phase 1 syntax fixes complete

Self-hosted compiler (selfhost/*.ludic), runtime, examples, editor tooling,
and docs. Phase 1 of the syntax-redesign cohesion pass has landed:
edge-system fix, signature-query, when-alias, and the documentation truth-pass.
Suite green (14/14), C-free bootstrap fixpoint holds.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tools/editors/jetbrains/build.gradle.kts

@@ -0,0 +1,96 @@
+import org.jetbrains.intellij.platform.gradle.TestFrameworkType
+import org.jetbrains.intellij.platform.gradle.IntelliJPlatformType
+
+plugins {
+    id("java")
+    id("org.jetbrains.kotlin.jvm") version "2.4.10"
+    // The IntelliJ Platform Gradle Plugin 2.x. The 1.x line (org.jetbrains.intellij)
+    // is superseded and does not run on current Gradle.
+    id("org.jetbrains.intellij.platform") version "2.18.1"
+}
+
+group = providers.gradleProperty("pluginGroup").get()
+version = providers.gradleProperty("pluginVersion").get()
+
+repositories {
+    mavenCentral()
+    intellijPlatform {
+        defaultRepositories()
+    }
+}
+
+dependencies {
+    testImplementation("junit:junit:4.13.2")
+    intellijPlatform {
+        // Community, deliberately: the plugin must work in the free IDEs, which
+        // is also why the language server is wired up through LSP4IJ rather
+        // than com.intellij.platform.lsp (Ultimate and friends only).
+        // useInstaller = false takes the Maven artifact (com.jetbrains.intellij.idea:ideaIC)
+        // instead of the .dmg/.tar.gz installer. Since 2025.x the Community installer is
+        // published as `idea-<version>`, not `ideaIC-<version>`, and the installer path
+        // cannot find it; the Maven coordinate is unaffected by that rename.
+        intellijIdeaCommunity(providers.gradleProperty("platformVersion").get()) {
+            useInstaller = false
+        }
+        bundledPlugin("org.intellij.plugins.markdown")
+        plugin("com.redhat.devtools.lsp4ij", providers.gradleProperty("lsp4ijVersion").get())
+        // JetBrains' Plugin Verifier CLI, used by the verifyPlugin task below
+        pluginVerifier()
+        // headless fixtures for the platform tests in src/test
+        testFramework(TestFrameworkType.Platform)
+    }
+}
+
+kotlin {
+    jvmToolchain(17)
+}
+
+intellijPlatform {
+    pluginConfiguration {
+        name = providers.gradleProperty("pluginName")
+        version = providers.gradleProperty("pluginVersion")
+        ideaVersion {
+            sinceBuild = providers.gradleProperty("pluginSinceBuild")
+            untilBuild = providers.gradleProperty("pluginUntilBuild")
+        }
+    }
+    // Compatibility is claimed up to pluginUntilBuild, so it gets checked
+    // against that IDE rather than assumed: `./gradlew verifyPlugin` runs
+    // JetBrains' own Plugin Verifier over the built artifact.
+    pluginVerification {
+        ides {
+            // The platform this is compiled against, which is also the newest
+            // that exists (2025.3 = build 253). until-build claims 262, which
+            // no released IDE reaches yet.
+            create(IntelliJPlatformType.IntellijIdeaCommunity, providers.gradleProperty("platformVersion").get()) {
+                useInstaller = false
+            }
+        }
+    }
+
+    buildSearchableOptions = false
+
+    // The platform's bytecode instrumenter only adds @NotNull assertions and
+    // compiles .form files. This plugin is Kotlin with no GUI forms, so it has
+    // nothing to instrument — and skipping it avoids the instrumenter's JBR
+    // probing, which fails on a plain JDK layout.
+    instrumentCode = false
+}
+
+// `./gradlew runIde` opens the Ludic repository itself, so the sandbox has real
+// .ludic files to look at and build/ludic-lsp sitting where the plugin expects.
+// Three levels up: jetbrains -> editors -> tools -> repository root. Getting
+// this wrong points the IDE at tools/, where no build/ludic-lsp exists, and the
+// language server then cannot find itself.
+val repoRoot: File = rootProject.projectDir.parentFile.parentFile.parentFile
+tasks.named<JavaExec>("runIde") {
+    args = listOf(repoRoot.absolutePath)
+}
+
+tasks.test {
+    useJUnit()
+    testLogging {
+        events("passed", "failed", "skipped")
+        showStandardStreams = false
+    }
+}