Implement NK-WP-0013 playbook capability contract

tools/playbook-capability-contract/README.md

@@ -0,0 +1,28 @@
+# Playbook Capability Contract Validator
+
+Executable checks for
+`canon/standards/playbook-capability-contract_v0.1.md`.
+
+Runtime dependency: Python 3.11+ with `PyYAML`. Fixture tests also
+require `pytest`.
+
+Validate a declaration:
+
+```bash
+python3 tools/playbook-capability-contract/playbook_contract_validator.py \
+  ../railiance-infra/capabilities/playbooks/railiance-infra.bootstrap-host.yaml
+```
+
+Validate and compose a sample scenario:
+
+```bash
+python3 tools/playbook-capability-contract/playbook_contract_validator.py \
+  ../railiance-infra/capabilities/playbooks/railiance-infra.bootstrap-host.yaml \
+  --scenario examples/playbook-capability-contract/scenario-s1-host-bootstrap.yaml
+```
+
+Run tests:
+
+```bash
+python3 -m pytest tools/playbook-capability-contract/tests
+```