Onboard tenant-engine to the staged-promotion contract

TEN-WP-0008. railiance/app.toml declares criticality=high, empty secrets,
isolated canary, and the live PostgreSQL digest as previous_stable.
Manifests render through kustomize (deploy/ and deploy/canary/). Stage 1
passed. Stage 2/3 Helm-only CLI gap requested as RAIL-BS-IN-0001 rather
than a dummy chart.

Assistant: grok
Assistant-Session: 01a04cea-e5e8-7081-a0fc-808ebbc35fa9

pyproject.toml

@@ -25,6 +25,7 @@ dev = [
     "pytest>=8.2,<9.0",
     "ruff>=0.6,<1.0",
     "pyyaml>=6.0,<7.0",
+    "jsonschema>=4.0,<5.0",
 ]
 
 [project.scripts]