chore: add changeset for workflow improvements (#52)

Author: sapientpants

.changeset/workflow-improvements.md

@@ -0,0 +1,11 @@
+---
+'agentic-node-ts-starter': patch
+---
+
+Optimize GitHub Actions workflows for better performance and maintainability
+
+- Extract reusable workflows for setup, validation, and security scanning
+- Parallelize PR validation jobs for ~50% faster feedback
+- Simplify publish workflow by removing unnecessary matrix strategy
+- Fix publish workflow to properly handle secrets in conditions
+- Reduce overall workflow code by ~25% through DRY principles