fix(P26): resolve multi-resource L1 ref ids in contract resolver

---ci---
project: acdl
phase: 26
milestone: v1.7
status: execute
---/ci---

The microservice pattern (and any L2 referencing multi-resource L1s like
vpc) failed at the adapter stage because the resolver emitted refs using
the child id (e.g. 'vpc') instead of the expanded sub-resource id (e.g.
'vpc-subnet'). The adapter's type_by_id table only knows the sub-resource
ids, so ref:vpc.subnet_ids was an unknown resource id.

Fix:
- contract_resolver.py: child_outputs now maps {outputName -> resourceId}
  instead of just the interface outputs dict. For multi-resource L1s, the
  ref uses the sub-resource id that produces the output. For single-resource
  L1s, the resourceId == childId (unchanged behavior).
- vpc interface.json: the subnet sub-resource output is 'subnet_ids'
  (matching the interface-level output name) instead of 'subnet_id'.
- adapter.py OUTPUT_MAP: aws:ec2:subnet now maps both 'subnet_ids' and
  'subnet_id' to 'id'.

Verification:
  - microservice pattern check-only: PASS (11 resources)
  - static-assets pattern check-only: PASS (4 resources)
  - platform check-only: PASS
  - full test suite: 266 passed

adapters/terraform/adapter.py

@@ -68,7 +68,7 @@ INPUT_MAP = {
 OUTPUT_MAP = {
     "aws:s3:bucket": {"bucket_arn": "arn", "bucket_name": "id"},
     "aws:ec2:vpc": {"vpc_id": "id"},
-    "aws:ec2:subnet": {"subnet_id": "id"},
+    "aws:ec2:subnet": {"subnet_ids": "id", "subnet_id": "id"},
     "aws:ec2:routetable": {},
     "aws:ecs:cluster": {"cluster_arn": "arn", "cluster_id": "id"},
     "aws:ecs:task_definition": {"task_def_arn": "arn"},