fix: Use baseVersion for SNAPSHOT path/URL resolution in FileSystemChecksumCalculator

[Copilot]

Maven SNAPSHOT artifacts downloaded from remote repositories have a timestamped version (e.g. 1.0-20231010.123456-1) in their filename, but the local repository directory is named using the base version (1.0-SNAPSHOT). The old code used getVersion() for directory path/URL construction, causing lookups to fail for remotely-resolved SNAPSHOTs.

Changes

• FileSystemChecksumCalculator: Use artifact.getBaseVersion() instead of artifact.getVersion() when constructing the remote repository URL path segment (directory uses base version; filename retains the timestamped version)
• LockFileFacade: Use pluginArtifact.getBaseVersion() for the directory segment when resolving the local POM path for SNAPSHOT plugins
• FileSystemChecksumCalculatorTest: Unit tests covering both cases:
  • SNAPSHOT artifact resolved URL uses baseVersion as directory (1.0-SNAPSHOT/my-artifact-1.0-20231010.123456-1.jar)
  • Non-SNAPSHOT artifact URL is unaffected

// Correct URL for a SNAPSHOT downloaded from remote:
https://repo.maven.apache.org/maven2/com/example/my-artifact/1.0-SNAPSHOT/my-artifact-1.0-20231010.123456-1.jar
//                                                             ^^^^^^^^^^^^ baseVersion as directory
//                                                                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ timestamped filename

---

🔒 GitHub Advanced Security automatically protects Copilot coding agent pull requests. You can protect all pull requests by enabling Advanced Security for your repositories. Learn more about Advanced Security.