Add CLAUDE.md for Claude Code guidance

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Overview
+
+The Doma Compile Plugin is a Gradle plugin that allows annotation processors to read Doma resources at compile-time. It supports both Java and Kotlin and is part of the Doma framework ecosystem.
+
+## Common Commands
+
+### Building the Plugin
+```bash
+./gradlew build
+```
+
+### Running Tests
+The plugin has three test suites that must be run in sequence:
+```bash
+# Build the plugin first
+./gradlew build
+
+# Test with Java
+cd compile-java-test && ./gradlew build && cd ..
+
+# Test with Kotlin
+cd compile-kotlin-test && ./gradlew build && cd ..
+
+# Test with mixed Java/Kotlin
+cd compile-mix-test && ./gradlew build && cd ..
+```
+
+### Code Formatting
+```bash
+# Apply code formatting (Google Java Format)
+./gradlew spotlessApply
+```
+
+### Running a Single Test
+```bash
+# In any test directory (compile-java-test, compile-kotlin-test, or compile-mix-test)
+./gradlew test --tests "example.GenerationTest"
+```
+
+### Publishing (for maintainers)
+```bash
+# Release a new version (from master branch only)
+./gradlew release
+
+# Publish to Gradle Plugin Portal (handled by CI for non-SNAPSHOT versions)
+./gradlew publishPlugins -Pgradle.publish.key=<key> -Pgradle.publish.secret=<secret>
+```
+
+## Architecture
+
+### Project Structure
+- **compile/**: Main plugin implementation
+  - `CompilePlugin.java`: Entry point that applies configurations
+  - `ConfigureJava.java`: Configures Java compilation to include resource directories in sourcepath
+  - `ConfigureKotlin.groovy`: Configures Kotlin/KAPT to include resource directories
+
+- **Test Projects**: Three separate Gradle projects for testing different scenarios
+  - `compile-java-test/`: Tests plugin with pure Java
+  - `compile-kotlin-test/`: Tests plugin with pure Kotlin  
+  - `compile-mix-test/`: Tests plugin with mixed Java/Kotlin
+
+### How the Plugin Works
+The plugin modifies the compilation classpath to allow Doma's annotation processor to read SQL resource files during compile-time. It:
+
+1. Adds resource directories to the Java compiler's sourcepath
+2. Adds the `-parameters` flag to preserve parameter names
+3. For Kotlin, configures KAPT with the same settings
+
+This is equivalent to manually configuring:
+```kotlin
+compileJava {
+    options.sourcepath = files(sourceSets.main.resources.srcDirs)
+    options.compilerArgs.add("-parameters")
+}
+
+kapt {
+    javacOptions {
+        option("--source-path", resourceDirs.join(File.pathSeparator))
+        option("-parameters")      
+    }
+}
+```
+
+### Resource File Convention
+Doma SQL resources follow a specific directory structure:
+- Location: `src/main/resources/META-INF/<package>/<DaoName>/`
+- SQL files: `<methodName>.sql` (e.g., `selectById.sql`)
+- Script files: `<methodName>.script` (e.g., `create.script`)
+
+### Dependencies and Versions
+- Java: Requires Java 17 or later
+- Gradle: Uses Gradle wrapper
+- Doma: Compatible with Doma 3.8 or later
+- Testing: JUnit 5 (managed via BOM)
+
+### CI/CD Pipeline
+GitHub Actions workflow (`.github/workflows/ci.yml`):
+1. Triggers on push/PR to master branch
+2. Uses JDK 21 on Ubuntu
+3. Builds plugin, then tests all three scenarios
+4. Auto-publishes non-SNAPSHOT versions to Gradle Plugin Portal
+
+### Plugin Configuration
+The plugin is published as `org.domaframework.doma.compile` and can be applied:
+```kotlin
+plugins {
+    id("org.domaframework.doma.compile") version "4.x.x"
+}
+```