Add changeset for archive path fix (Fission-AI#587)

Author: TabishB

.changeset/archive-path-fix.md

@@ -0,0 +1,7 @@
+---
+"@fission-ai/openspec": patch
+---
+
+### Bug Fixes
+
+- Fixed incorrect archive path in onboarding documentation — the template now shows the correct path `openspec/changes/archive/YYYY-MM-DD-<name>/` instead of the incorrect `openspec/archive/YYYY-MM-DD--<name>/`