Bump smoke default to v0.3.1

The daily smoke workflow has been resolving the deliberately-old
0.2.0 artefact since it was first wired up. That's still useful
('the oldest released version stays resolvable on Maven Central')
but the more useful regression check is against the latest
release.

Bump the in-build.xml default from 0.2.0 to 0.3.1, with an
inline comment noting that the bump should happen in the same
commit that tags a new release. The override (-Dedtf.version=)
still works for ad-hoc runs against historical versions if you
ever need to verify a specific older release.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: jeffreyameyer

smoke/build.xml

@@ -9,8 +9,10 @@
 <project name="edtf-java-smoke" basedir="." default="test"
          xmlns:ivy="antlib:org.apache.ivy.ant">
 
-    <!-- Library version under test. Override with -Dedtf.version=X.Y.Z. -->
-    <property name="edtf.version" value="0.2.0"/>
+    <!-- Library version under test. Override with -Dedtf.version=X.Y.Z.
+         Bump this in the same commit that tags a new release so the
+         daily smoke run always exercises the latest published artefact. -->
+    <property name="edtf.version" value="0.3.1"/>
 
     <property name="lib.dir"     value="lib"/>
     <property name="build.dir"   value="build"/>