Add Railiance Stage 2 deploy observe tooling

tools/README_tools.md

@@ -59,6 +59,11 @@ This model emphasizes:
 
 ---
 
+
+### `railiance-stage2`
+- Backs `bin/railiance deploy --stage 2` and `bin/railiance observe --stage 2`.
+- Emits non-secret JSON plans/results for canary deployment and observation.
+
 ### `railiance-run`
 - Executes Stage 1 local validation from `railiance/app.toml`.
 - Emits a `railiance.run-result.v1` JSON result without command logs or secrets.