docs: add CLAUDE.md with build commands and Struts 7 conventions

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.
+
+## What this is
+
+A Maven multi-module (reactor) project of standalone Apache Struts 7 example webapps that back the
+Getting Started tutorials at https://struts.apache.org. Each module is an independent `.war`; modules
+do not depend on each other. Issues are tracked in JIRA project `WW`.
+
+## Commands
+
+Java 17 (CI also builds on 21). Use the wrapper `./mvnw` or `mvn`.
+
+```bash
+./mvnw -e clean package                               # build every module's .war (README's command)
+./mvnw -B test                                        # what CI runs (.github/workflows/maven.yml)
+./mvnw -pl blank test                                 # tests for one module
+./mvnw -pl blank test -Dtest=LoginTest                # single test class
+./mvnw -pl blank test -Dtest=LoginTest#testLoginSubmit # single test method
+./mvnw -pl helloworld jetty:run                       # run one example at http://localhost:8080/<artifactId>/
+./mvnw -Pdependency-check verify                      # OWASP check, fails on CVSS >= 7; suppressions in src/etc/project-suppression.xml
+(cd quarkus && ../mvnw clean compile quarkus:dev)     # quarkus module runs on Quarkus, not Jetty, and uses FreeMarker (no JSP)
+```
+
+Only a few modules have tests (`blank`, `unit-testing`, `rest-angular`, `text-provider`); most
+examples are verified by running them. Many modules carry a `README.txt`/`README.md` with the
+tutorial link and the URL to open.
+
+## Structure
+
+- The root `pom.xml` is the single source of versions: `struts2.version`, `log4j2.version`,
+  `jetty-plugin.version`, Jackson BOM, Jakarta Servlet/JSP APIs (`provided`). Every module inherits
+  `struts2-core`, `log4j-core` and the servlet/JSP APIs; modules add only the Struts plugins they
+  demonstrate (convention, json, rest, spring, tiles, junit, bean-validation, jasperreports, …).
+- A new module must be added to `<modules>` in the root `pom.xml` and normally copies the
+  `jetty-maven-plugin` block from an existing module (context path `/${project.artifactId}`).
+- Typical module layout: actions in `src/main/java`, `struts.xml` + `log4j2.xml` + message bundles
+  in `src/main/resources`, JSPs and `WEB-INF/web.xml` under `src/main/webapp`. Modules using the
+  convention plugin (`annotations`, `rest-angular`, `text-provider`, `unknown-handler`) configure
+  actions via annotations/naming instead of `struts.xml`.
+
+## Struts 7 conventions to preserve
+
+These examples are teaching material, so keep config files on the current standard:
+
+- Struts config DOCTYPE: `struts-6.5.dtd` (`https://struts.apache.org/dtds/struts-6.5.dtd`);
+  `web.xml` on `web-app_6_0.xsd`, `version="6.0"`; Jakarta (`jakarta.*`) namespaces only.
+- **`@StrutsParameter` is required** for request parameters to reach an action
+  (`struts.parameters.requireAnnotations=true` is the default). A missing annotation silently drops
+  the parameter rather than failing. Rules:
+  - Only the action class is checked; model beans (`Person`, `MessageStore`, …) need no annotation.
+  - Top-level param (`name`) → annotate the **setter**.
+  - Nested param (`personBean.firstName`, `items[0]`) → annotate the **getter** with
+    `depth = N` (number of `.`/`[` in the longest name under that root). Annotating the setter
+    has no effect for nested params.
+  - The same rules apply to JSON/REST plugin bodies and `CookieInterceptor`.
+- Leave existing `struts.allowlist.*` settings in place even when they look redundant.
+- Refer to the framework as "Apache Struts", not "Struts 2".
+
+Design notes and plans for larger changes live in `docs/superpowers/` (specs and plans).