Fix #134: add regression test for multi-digit version extraction

[elharo]

Closes #134

Summary

Issue #134 reports that FilenameExposer truncates multi-digit version numbers (e.g. my-lib-12.3.4.jar would yield version 2.3.4).

Investigation showed the described behavior does not reproduce. FilenameExposer uses filename.substring(mat.end() - 1), where mat.end() - 1 is the index of the first digit matched by the -\\d pattern. substring() therefore includes the full multi-digit version, so my-lib-12.3.4.jar correctly yields 12.3.4, my-lib-10.jar yields 10, etc. No source change is required.

Test

Adds FilenameExposerTest, which builds JARs in memory with version-specific filenames and asserts FilenameExposer extracts the full version:

• my-lib-12.3.4.jar → 12.3.4
• my-lib-10.jar → 10
• my-lib-21.5.7.jar → 21.5.7
• my-lib-9.0.jar → 9.0
• my-lib.jar → no version

These tests document the expected behavior and guard against regressions.