Add AGENTS.md with project guidance for AI coding agents

AGENTS.md

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+# AGENTS.md
+
+This file provides guidance to AI coding agents working with code in this repository.
+
+## What is Showkase?
+
+Showkase is an annotation-processor-based Android library for organizing and browsing Jetpack Compose UI components, colors, and typography. It processes `@ShowkaseComposable`, `@ShowkaseColor`, `@ShowkaseTypography`, and `@Preview` annotations to generate a browsable UI catalog and screenshot test files.
+
+## Build Commands
+
+```bash
+# Build entire project
+./gradlew build
+
+# Run all checks (unit tests + detekt linting)
+./gradlew check
+
+# Run checks with KSP instead of KAPT (default is KAPT)
+./gradlew check -PuseKsp=true
+
+# Run detekt linting only
+./gradlew detekt
+
+# Build a single module
+./gradlew :showkase-processor:build
+
+# Run processor unit tests
+./gradlew :showkase-processor:test
+
+# Run a single test class
+./gradlew :showkase-processor:test --tests ShowkaseMetadataTest
+
+# Run a single test method
+./gradlew :showkase-processor:test --tests ShowkaseMetadataTest.isTopLevelFunction
+
+# Paparazzi screenshot tests
+./gradlew :showkase-screenshot-testing-paparazzi-sample:verifyPaparazziDebug -PuseKsp=true
+
+# Instrumented tests (requires emulator/device)
+./gradlew connectedCheck
+```
+
+## Architecture
+
+### Module Structure
+
+- **`showkase-annotation`** — Pure Java library defining the annotations (`@ShowkaseComposable`, `@ShowkaseColor`, `@ShowkaseTypography`, `@ShowkaseRoot`). No Android dependencies.
+- **`showkase-processor`** — Annotation processor (supports both KSP and KAPT) that processes annotations and generates browser metadata, extension functions, and screenshot test files. Uses XProcessing (`androidx.room:room-compiler-processing`) as a unified abstraction over KSP/KAPT and KotlinPoet for code generation.
+- **`showkase`** — Android library providing the runtime UI browser (`ShowkaseBrowserActivity` and Compose screens). Contains the `Showkase` object, `ShowkaseProvider` interface, and data models (`ShowkaseBrowserComponent`, `ShowkaseBrowserColor`, `ShowkaseBrowserTypography`).
+- **`showkase-screenshot-testing`** / **`showkase-screenshot-testing-paparazzi`** / **`showkase-screenshot-testing-shot`** — Screenshot testing integrations for Paparazzi and Shot frameworks.
+- **`showkase-processor-testing`** — Test harness for the annotation processor using kotlin-compile-testing and XProcessing testing APIs.
+- **`sample`**, **`sample-submodule`**, **`sample-submodule-2`** — Sample app demonstrating multi-module usage.
+
+### Annotation Processing Flow
+
+1. `ShowkaseProcessor` (entry point) extends `BaseProcessor` which unifies KSP and KAPT via XProcessing.
+2. Processing rounds collect annotated elements into `ShowkaseMetadata` models (components, colors, typography).
+3. Writer classes generate code:
+   - `ShowkaseBrowserWriter` → `ShowkaseProvider` implementation
+   - `ShowkaseBrowserPropertyWriter` → individual component/color/typography properties
+   - `ShowkaseExtensionFunctionsWriter` → `Showkase.getBrowserIntent()` and `Showkase.getMetadata()`
+   - `ShowkaseScreenshotTestWriter` / `PaparazziShowkaseScreenshotTestWriter` → screenshot test files
+
+### Multi-Module Support
+
+One module declares `@ShowkaseRoot` to aggregate UI elements from all dependent modules. The processor generates `@ShowkaseRootCodegen`-annotated code in the root module's package, collecting metadata from all submodules.
+
+### KSP vs KAPT
+
+- Default is KAPT; pass `-PuseKsp=true` to use KSP.
+- The `useKsp` property in `build.gradle` files controls which plugin is applied in sample/test modules.
+- Processor compiler options: `skipPrivatePreviews`, `requireShowkaseComposableAnnotation`, `multiPreviewType` (KAPT only for custom preview annotations).
+
+## Testing
+
+- **Unit tests**: JUnit 4 with Strikt assertions. Processor tests use kotlin-compile-testing.
+- **Screenshot tests**: Paparazzi (JVM-based, no device needed) and Shot (requires emulator).
+- **Instrumented tests**: Standard Android instrumented tests via `connectedCheck`.
+- Processor tests in `showkase-processor-testing` require JDK 16+ JVM args for compiler module access (configured in its `build.gradle`).
+
+## Code Style
+
+- Kotlin official code style (`kotlin.code.style=official`)
+- Detekt for static analysis (config: `detekt/detekt.yml`)
+- Java 17 toolchain

CLAUDE.md

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+AGENTS.md