Update Gradle Version Formatting Validation

[jesswrd]

Updated the Gradle version formatting validation with a stricter regex. Previously passed on invalid versions.

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[gemini-code-assist]

Code Review

This pull request updates the Gradle version validation to use a more specific regular expression and provides a more detailed error message for invalid formats. The corresponding tests have been improved to cover more invalid version scenarios. While these changes are good, a new constant agpForExamples has been added but is not used anywhere in the command's logic, which should be addressed.