Add documentation for maven.build.cache.cacheCompile parameter

Document the new cacheCompile configuration parameter that controls
whether compile-only builds create cache entries:

- Add parameter to the command line flags table in parameters.md
- Add how-to section explaining when to disable compile caching

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: cowwoc

src/site/markdown/how-to.md

@@ -227,3 +227,18 @@ Set attribute `excludeDependencies` to `true` in `input/plugins/plugin` section:
       </plugins>
     </input>
 ```
+
+### I want to disable caching of compile-only builds
+
+By default, the cache extension saves build outputs when running compile-only phases (like `mvn compile` or `mvn test-compile`).
+This allows subsequent builds to restore compiled classes without recompilation. To disable this behavior and only cache
+builds that reach the package phase or later:
+
+```shell
+mvn compile -Dmaven.build.cache.cacheCompile=false
+```
+
+This is useful when:
+* You want to ensure cache entries always contain packaged artifacts (JARs, WARs, etc.)
+* Your workflow relies on artifacts being available in the local repository
+* You prefer the traditional behavior where only complete builds are cached

src/site/markdown/parameters.md

@@ -39,6 +39,7 @@ This document contains various configuration parameters supported by the cache e
 | `-Dmaven.build.cache.skipCache=(true/false)`               | Skip looking up artifacts in caches. Does not affect writing artifacts to caches, disables only reading when set to `true`               | May be used to trigger a forced rebuild when matching artifacts do exist in caches |
 | `-Dmaven.build.cache.skipSave=(true/false)`            | Skip writing build result in caches. Does not affect reading from the cache.               | Configuring MR builds to benefits from the cache, but restricting writes to the `master` branch |
 | `-Dmaven.build.cache.mandatoryClean=(true/false)`          | Enable or disable the necessity to execute the `clean` phase in order to store the build result in cache                                  | Reducing the risk to save "wrong" files in cache in a local dev environnement      |
+| `-Dmaven.build.cache.cacheCompile=(true/false)`            | Cache compile phase outputs (classes, test-classes, generated sources). When enabled (default), compile-only builds create cache entries that can be restored by subsequent builds. When disabled, caching only occurs during package phase or later. | Performance optimization for incremental builds                                    |
 
 ### Project-level properties