chore: add changeset for opsx:verify skill and bug fixes (Fission-AI#502)

* Add changeset for opsx:verify skill and bug fixes

* Update changeset to follow template format

Author: TabishB

.changeset/opsx-verify-skill.md

@@ -0,0 +1,13 @@
+---
+"@fission-ai/openspec": minor
+---
+
+### New Features
+
+- **`/opsx:verify` command** — Validate that change implementations match their specifications
+
+### Bug Fixes
+
+- Fixed vitest process storms by capping worker parallelism
+- Fixed agent workflows to use non-interactive mode for validation commands
+- Fixed PowerShell completions generator to remove trailing commas