✨ feat(playbook): auto-inject AGENTS.md into CLAUDE.md

When any sync action runs and the target project already has a CLAUDE.md,
automatically insert @AGENTS.md / @AGENT_RULES.md import block so
Claude Code picks up the same rules as Codex without manual setup.

- Add sync_claude_md() called at end of sync_agents_template()
- Uses <!-- playbook:claude:start/end --> block markers for idempotent updates
- Skips if no CLAUDE.md exists (Codex users unaffected)
- Skips if @AGENTS.md already present (manual setups respected)
- Add 4 tests covering: no file, append, update block, already-referenced

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/cli/test_playbook_cli.py

@@ -487,5 +487,101 @@ skills = ["style-cleanup"]
                 root, agents_home, f"{CUSTOM_DEPLOY_ROOT}/docs"
             )
 
+    def test_sync_claude_md_skips_when_no_claude_md(self):
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            config_body = f"""
+[playbook]
+project_root = "{tmp_dir}"
+deploy_root = "{CUSTOM_DEPLOY_ROOT}"
+
+[sync_memory_bank]
+project_name = "Demo"
+"""
+            config_path = Path(tmp_dir) / "playbook.toml"
+            config_path.write_text(config_body, encoding="utf-8")
+
+            result = run_cli("-config", str(config_path))
+
+            self.assertEqual(result.returncode, 0)
+            self.assertFalse((Path(tmp_dir) / "CLAUDE.md").exists())
+
+    def test_sync_claude_md_appends_block_to_existing_claude_md(self):
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            claude_md = Path(tmp_dir) / "CLAUDE.md"
+            claude_md.write_text("# My project\n\nSome existing content.\n", encoding="utf-8")
+
+            config_body = f"""
+[playbook]
+project_root = "{tmp_dir}"
+deploy_root = "{CUSTOM_DEPLOY_ROOT}"
+
+[sync_memory_bank]
+project_name = "Demo"
+"""
+            config_path = Path(tmp_dir) / "playbook.toml"
+            config_path.write_text(config_body, encoding="utf-8")
+
+            result = run_cli("-config", str(config_path))
+
+            self.assertEqual(result.returncode, 0)
+            text = claude_md.read_text(encoding="utf-8")
+            self.assertIn("@AGENTS.md", text)
+            self.assertIn("@AGENT_RULES.md", text)
+            self.assertIn("<!-- playbook:claude:start -->", text)
+            self.assertIn("Some existing content.", text)
+
+    def test_sync_claude_md_updates_existing_block(self):
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            claude_md = Path(tmp_dir) / "CLAUDE.md"
+            claude_md.write_text(
+                "# My project\n\n"
+                "<!-- playbook:claude:start -->\n"
+                "@AGENTS.md\n"
+                "<!-- playbook:claude:end -->\n",
+                encoding="utf-8",
+            )
+
+            config_body = f"""
+[playbook]
+project_root = "{tmp_dir}"
+deploy_root = "{CUSTOM_DEPLOY_ROOT}"
+
+[sync_memory_bank]
+project_name = "Demo"
+"""
+            config_path = Path(tmp_dir) / "playbook.toml"
+            config_path.write_text(config_body, encoding="utf-8")
+
+            result = run_cli("-config", str(config_path))
+
+            self.assertEqual(result.returncode, 0)
+            text = claude_md.read_text(encoding="utf-8")
+            self.assertIn("@AGENTS.md", text)
+            self.assertIn("@AGENT_RULES.md", text)
+            self.assertEqual(text.count("<!-- playbook:claude:start -->"), 1)
+
+    def test_sync_claude_md_skips_when_already_references_agents(self):
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            claude_md = Path(tmp_dir) / "CLAUDE.md"
+            original = "# My project\n\n@AGENTS.md\n"
+            claude_md.write_text(original, encoding="utf-8")
+
+            config_body = f"""
+[playbook]
+project_root = "{tmp_dir}"
+deploy_root = "{CUSTOM_DEPLOY_ROOT}"
+
+[sync_memory_bank]
+project_name = "Demo"
+"""
+            config_path = Path(tmp_dir) / "playbook.toml"
+            config_path.write_text(config_body, encoding="utf-8")
+
+            result = run_cli("-config", str(config_path))
+
+            self.assertEqual(result.returncode, 0)
+            self.assertEqual(claude_md.read_text(encoding="utf-8"), original)
+
+
 if __name__ == "__main__":
     unittest.main()