chore: add changeset for validation auto-fix

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: himerus

.changeset/validation-auto-fix.md

@@ -0,0 +1,6 @@
+---
+'helixir': minor
+'@helixir/core': minor
+---
+
+feat: add auto-fix suggestions to validation summary — agents get corrected code alongside each issue