add CLAUDE.md with build commands and architecture overview

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: asolntsev

.gitignore

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 /.gradle
 /.idea
 /out
-build
+build
+/.claude/settings.local.json

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.
+
+## Project
+
+AssertLog is a Java library for unit-testing logging. It intercepts log output during tests and provides assertion methods to verify what was (or was not) logged.
+
+Group ID: `com.codeborne.assertlog` | Current version: `0.2-SNAPSHOT`
+
+## Commands
+
+```bash
+./gradlew test                             # run all tests (default task also runs clean)
+./gradlew clean test                       # clean build then test (what CI runs)
+./gradlew :assertlog-log4j-junit4:test --tests "org.assertlog.PetClinicTest#info"  # single test
+./gradlew build                            # compile + test + jar
+```
+
+Tests only run classes matching `org/assertlog/**/*` (configured in root `build.gradle`).
+
+## Module Structure
+
+Two submodules declared in `settings.gradle`:
+
+- **`assertlog-core`** — shared types only; currently just `OriginalLogsPolicy` enum (`SHOW`/`HIDE`)
+- **`assertlog-log4j-junit4`** — Log4j 1.x + JUnit 4 integration; depends on `assertlog-core`
+
+Each submodule has its own `build.gradle` for dependencies. Root `build.gradle` applies shared config (Java 8 source/target, UTF-8 encoding, test logging). `gradle/deploy.gradle` handles Maven Central publishing via `uploadArchives` (requires `signing.keyId` property).
+
+## Key Class: MockLogging
+
+`MockLogging` (`assertlog-log4j-junit4`) is a JUnit 4 `ExternalResource` rule that:
+
+1. **`before()`** — saves the root Log4j logger's state, sets the configured log level, removes existing appenders if `policy == HIDE`, then adds a capturing appender that feeds into an internal `ArrayDeque<LoggingEvent>`
+2. **`after()`** — removes the capturing appender and restores the original level and appenders
+
+Assertion methods consume events from the queue (ordered, dequeue semantics) except:
+- `assertLoggedInAnyOrder` / `assertLogged(Pattern)` / `assertNotLogged(Pattern)` — search without requiring order
+- `assertNoMoreLogs()` — fails if the queue is not empty (typically called in `@After`)
+
+`assertNotLogged` and `assertLogged(Pattern)` (the non-consuming overload) **must be called before** the dequeue-based `assertLogged` methods, as the queue is mutated.
+
+## Adding New Integrations
+
+The pattern for a new logging framework or test runner is:
+1. Create a new submodule (e.g., `assertlog-logback-junit5`)
+2. Add it to `settings.gradle`
+3. Implement an equivalent of `MockLogging` using the target framework's extension mechanism
+4. Depend on `assertlog-core` for shared types