docs: Add Gradle wrapper documentation to build prerequisites

Author: margaretkennedy

docs/groovy/getting-started/launch-build.md

@@ -35,6 +35,16 @@ java --version
 > [!NOTE]
 > The Java build process uses [Gradle Auto Provisioning](https://docs.gradle.org/current/userguide/toolchains.html#sec:provisioning) to download and use the appropriate Java version for building and testing.
 
+### Gradle
+
+Deephaven uses [Gradle](https://gradle.org/) as its build tool. You do not need to install Gradle manually — the repository includes the [Gradle Wrapper](https://docs.gradle.org/current/userguide/gradle_wrapper.html) (`gradlew` / `gradlew.bat`), which downloads and runs the correct version of Gradle automatically.
+
+You can verify the wrapper is present after cloning:
+
+```bash
+ls gradlew
+```
+
 ### Version control
 
 Deephaven highly recommends using a version control system to clone the [deephaven-core repository](https://github.com/deephaven/deephaven-core). The most popular and common option is [git](https://git-scm.com/); this guide uses it to clone the repository.

docs/python/getting-started/launch-build.md

@@ -37,6 +37,16 @@ java --version
 > [!NOTE]
 > The Java build process uses [Gradle Auto Provisioning](https://docs.gradle.org/current/userguide/toolchains.html#sec:provisioning) to download and use the appropriate Java version for building and testing.
 
+### Gradle
+
+Deephaven uses [Gradle](https://gradle.org/) as its build tool. You do not need to install Gradle manually — the repository includes the [Gradle Wrapper](https://docs.gradle.org/current/userguide/gradle_wrapper.html) (`gradlew` / `gradlew.bat`), which downloads and runs the correct version of Gradle automatically.
+
+You can verify the wrapper is present after cloning:
+
+```bash
+ls gradlew
+```
+
 ### Python
 
 It is recommended you stay up-to-date with the latest Python version. Deephaven requires Python **3.9** or later. You can check your Python version with: