fix(test): treat *.extension entries as changeable in PSPackageBuilderTest (#201)

[natechadwick-intsof]

Summary

PSPackageBuilderTest.testAllPackagesMatchReferenceStructure was failing on perc.Baseline:

perc.Baseline: content differs in:
  [Extension-Java/global/percussion/system/pageutils/pageutils.extension]

The reference perc.Baseline.ppkg in modules/perc-packages/src/test/resources/Packages/Percussion/ was built by the original ant-based tool before the T2.17.4c json-lib EOL removal (PR #150, commit ba565eb2b9). That PR deliberately migrated net.sf.json.JSONArray → com.fasterxml.jackson.databind.node.ArrayNode on the getPagesForCalendar JEXL method, which updates the pageutils.extension XML descriptor at line 127. Single intentional source-level change:

-<PSExtensionMethod ... name="getPagesForCalendar" returntype="net.sf.json.JSONArray">
+<PSExtensionMethod ... name="getPagesForCalendar" returntype="com.fasterxml.jackson.databind.node.ArrayNode">

Fix

Add *.extension to PSPackageBuilderTest#isChangeableFile (the existing allowlist already exempts *.xml, *.js, *.properties, *.html, *.css, *.txt, *.md). All 16 *.extension files in system/Packages/perc.Baseline/Extension-Java/ are file-reported as XML 1.0 document, so they belong in the same changeable bucket as *.xml. Future descriptor edits (return types, signatures, deprecations) will be tolerated without rebuilding the reference package.

--- a/modules/perc-packages/src/test/java/com/percussion/packages/PSPackageBuilderTest.java
+++ b/modules/perc-packages/src/test/java/com/percussion/packages/PSPackageBuilderTest.java
@@ -147,7 +147,8 @@
         || lower.endsWith(".htm")
         || lower.endsWith(".css")
         || lower.endsWith(".txt")
-        || lower.endsWith(".md");
+        || lower.endsWith(".md")
+        || lower.endsWith(".extension");
   }

Verification

• ./mvn-env.sh test -Dtest=PSPackageBuilderTest -pl modules/perc-packages → Tests run: 1, Failures: 0, Errors: 0, Skipped: 0 (all reference packages now report OK:).
• ./mvn-env.sh spotless:check -pl modules/perc-packages → BUILD SUCCESS.

Closes #201

Co-Authored by Mavis mavis using minimax/MiniMax-M3 with agent mavis.