fix: lower selftest extension version requirement to >=0.0.128

Author: kanfil

extensions/selftest/extension.yml

@@ -8,7 +8,7 @@ extension:
   repository: https://github.com/github/spec-kit
   license: MIT
 requires:
-  speckit_version: ">=0.2.0"
+  speckit_version: ">=0.0.128"
 provides:
   commands:
     - name: speckit.selftest.extension