chore: remove AI agent configs from git, add to gitignore

Remove AGENTS.md and CLAUDE.md from version control.

Add dev environment readiness spec.

Author: Slashmsu

.gitignore

@@ -92,4 +92,8 @@ codecov.SHA256SUM*
 example-audit-report.json
 
 # Gitnexus
-.gitnexus/
+.gitnexus/
+
+# AI agent configs
+AGENTS.md
+CLAUDE.md