feat(P40): contract interpolation + environment JSON schema

---ci---
project: acdl
phase: 40
milestone: v1.9
status: execute
---/ci---

Phase 40 — contract-interpolation (REQ-103, REQ-104, D-081):

Interpolation:
- core/contract_resolver.py: _expand_vars(value, context) recursively
  expands ${env.<field>} + ${contract.<field>} tokens (dotted paths
  supported, e.g. ${env.state_backend.bucket}). Unknown tokens raise
  ValueError (fail loud). Expansion is post-schema-validation,
  pre-IR-resolution.
- resolve() accepts environment_override (D-088) — overrides the
  contract's environment field BEFORE schema validation so interpolation
  context is consistent.
- env context loaded via _load_env (self-contained, works as script +
  package import); 'environment' alias for env 'name' so
  ${env.environment} resolves.

Environment schema + bindings:
- schemas/environment.schema.json (draft 2020-12): name, account_id,
  region, state_backend, network, runner_role_arn, autonomy, confidence_threshold.
- core/environments/qa.json, prod.json, dr.json placeholder bindings
  (attested, thresholds 0.75/0.90/0.95, placeholder account_id with
  stderr warning at load).
- core/environment_check.py: load(env_name) helper + placeholder warning.

Sample contracts:
- contracts/static-assets.yaml + microservice.yaml use
  acdl-${env.environment}-${contract.module}-${env.account_id}-${env.region}
  naming pattern (region + account id + environment).

Tests: +35 (test_environment_schema.py, test_interpolation.py,
test_sample_contracts_interpolate.py). 406 passed; run_ci.sh green;
run_platform.sh --check-only green. Existing fixture-based tests
preserved (instance.json static fixtures unaffected).

contracts/microservice.yaml

@@ -1,13 +1,14 @@
 # ACDL sample consumer contract — microservice module (dev)
 #
 # Reference example for an ECS Fargate microservice deployment.
-# This contract declares only the inputs the composition wires reference
-# (bucket_name, region) plus a representative image/port.
+# Interpolation (D-081): bucket_name uses the naming pattern that includes
+# region, aws account id, and environment:
+#   acdl-${env.environment}-${contract.module}-${env.account_id}-${env.region}
 uses: acdl/pipelines/deploy.yaml@v1.6
 module: microservice
 environment: dev
 inputs:
-  bucket_name: acdl-microservice-demo
-  region: us-east-1
+  bucket_name: acdl-${env.environment}-${contract.module}-${env.account_id}-${env.region}
+  region: ${env.region}
   image: public.ecr.aws/docker/library/nginx:latest
   port: 80

contracts/static-assets.yaml

@@ -8,10 +8,16 @@
 #
 # Validated against schemas/contract.schema.json.
 # Resolved by core/contract_resolver.py to a Target Stack instance.
+#
+# Interpolation (D-081): ${env.<field>} + ${contract.<field>} tokens are
+# expanded by the resolver from the environment onboarding JSON. The
+# bucket_name below demonstrates the naming pattern that includes region,
+# aws account id, and environment:
+#   acdl-${env.environment}-${contract.module}-${env.account_id}-${env.region}
 
 uses: acdl/pipelines/deploy.yaml@v1.6
 module: static-assets
 environment: dev
 inputs:
-  bucket_name: acdl-spike-bucket
-  region: us-east-1
+  bucket_name: acdl-${env.environment}-${contract.module}-${env.account_id}-${env.region}
+  region: ${env.region}