✨ feat(playbook): add no_backup deploy controls

remove obsolete main_language placeholders and language summary template text

limit generated .agents guidance to configured langs and normalize AGENT_RULES trailing newlines

document install_skills no_backup behavior and refresh tests for deployment links and sync flows

tests/test_no_backup_flags.py

@@ -74,6 +74,36 @@ no_backup = true
             git_backups = list(root.glob(".gitattributes.bak.*"))
             self.assertEqual(git_backups, [])
 
+    def test_install_skills_no_backup_replaces_existing_skill_without_backup(self):
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            root = Path(tmp_dir)
+            skills_root = root / "agents" / "skills"
+            existing = skills_root / "brainstorming"
+            existing.mkdir(parents=True)
+            (existing / "stale.txt").write_text("old", encoding="utf-8")
+
+            config_body = f"""
+[playbook]
+project_root = "{tmp_dir}"
+deploy_root = "{DEFAULT_DEPLOY_ROOT}"
+
+[install_skills]
+agents_home = "{root / 'agents'}"
+mode = "list"
+skills = ["brainstorming"]
+no_backup = true
+"""
+            config_path = root / "playbook.toml"
+            config_path.write_text(config_body, encoding="utf-8")
+
+            result = run_cli("-config", str(config_path))
+            self.assertEqual(result.returncode, 0, msg=result.stderr)
+
+            backups = list(skills_root.glob("brainstorming.bak.*"))
+            self.assertEqual(backups, [])
+            self.assertFalse((existing / "stale.txt").exists())
+            self.assertTrue((existing / "SKILL.md").is_file())
+
 
 if __name__ == "__main__":
     unittest.main()