feat(P2): env-transition detect-and-destroy — REQ-282..287

- core/env_transition.py: detect_prior_env() + record_applied_env() via DynamoDB nova-contracts table (REQ-282,283)
- scripts/run_platform.sh Step 0b: detect env change, destroy prior env (deletion_protection=false, terraform init -reconfigure + destroy), emit ENV_DESTROYED evidence event, fail closed on destroy failure (REQ-284)
- scripts/run_platform.sh: record applied env after successful apply (REQ-285)
- .github/workflows/deploy.yml: pass NOVA_CONSUMER_REPO to run_platform.sh (REQ-286)
- adapters/terraform/adapter.py: doc comment on env-scoped state key (REQ-287)

No orphan path: if destroy fails, pipeline exits non-zero (no apply runs).

---ci---
project: acdl
phase: 2
milestone: v1.24
status: execute
requirements: [REQ-282,REQ-283,REQ-284,REQ-285,REQ-286,REQ-287]
---/ci---

adapters/terraform/adapter.py

@@ -115,6 +115,9 @@ def adapt(stack_instance, out_dir):
     environment = stack.get("environment", "dev")
     account_id = env.get_env("AWS_ACCOUNT_ID", "581513795199")
     state_bucket = f"nova-tfstate-{account_id}-us-east-1"
+    # State key is env-scoped (v1.24 REQ-287): the {environment} segment lets
+    # the env-transition detect-and-destroy step target the PRIOR env's state
+    # without affecting the new env. No orphan path on environment promotion.
     terraform_tf = (
         'terraform {\n'
         '  required_version = ">= 1.9, < 1.10"\n'