ci: drop the version-named SSM layer parameter

Every merge to main has failed at deploy-beta since the v1.1.0 revert
(2026-07-10) with:

  Resource of type 'AWS::SSM::Parameter' with identifier
  '/lambda-web-adapter/layer/x86_64/1.0.1' already exists. (AlreadyExists)

The parameter's Name embedded ${CargoPkgVersion}, so a version change forces
CloudFormation to replace the resource, and UpdateReplacePolicy: Retain left
the old name behind un-managed. Releasing 1.1.0 orphaned /x86_64/1.0.1;
reverting to 1.0.1 then tried to create that exact name and hit the orphan.
Rollback restores the 1.1.0 name, so the next deploy repeats it — a permanent
wedge, not a flake. It also took e2e-test-zip and e2e-test-oci down with it
(both `needs: deploy-beta`), so main had no e2e coverage for two months.

Removing the resource is the fix rather than dropping UpdateReplacePolicy:
with only the current version ever tracked, the per-version parameter holds
the same value as the /latest parameter beside it, so it earns nothing. The
alternative — writing it with `aws ssm put-parameter --overwrite` from the
workflow — needs ssm:PutParameter added to the PipelineExecutionRole in every
beta, gamma, prod, and China account, which today grants only ssm:GetParameters
on /lambda-web-adapter/e2e/*.

Nothing reads a per-version parameter: the only consumer of either parameter is
tests/e2e_tests/fixtures/go-httpbin-zip/template.yaml, which reads
/lambda-web-adapter/layer/x86_64/latest. That one keeps its static name, so it
updates in place and can never collide.

No parameter is deleted by this change. DeletionPolicy: Retain applies when a
resource is removed from the template, so the currently-tracked names are kept
as the historical pointers, and the layer Description still records the version
for `aws lambda list-layer-versions`.

Author: bnusunny

template-arm64.yaml

@@ -39,15 +39,10 @@ Resources:
       Type: String
       Value: !Ref LambdaAdapterLayerArm64
 
-  LambdaAdapterLayerArm64VersionParameter:
-    Type: AWS::SSM::Parameter
-    DeletionPolicy: Retain
-    UpdateReplacePolicy: Retain
-    Properties:
-      Name: !Sub '/lambda-web-adapter/layer/arm64/${CargoPkgVersion}'
-      Description: !Sub 'Layer ARN for the latest Lambda Web Adapter Arm64 Layer: ${CargoPkgVersion}'
-      Type: String
-      Value: !Ref LambdaAdapterLayerArm64
+  # A per-version parameter (/lambda-web-adapter/layer/arm64/<CargoPkgVersion>) used to
+  # live here. See the matching comment in template-x86_64.yaml for why it was removed:
+  # a Name change replaces the parameter, and UpdateReplacePolicy: Retain orphaned the
+  # old name, so re-deploying an already-used version failed with AlreadyExists.
 
 Outputs:
   LambdaAdapterLayerArm64Arn:

template-x86_64.yaml

@@ -39,15 +39,14 @@ Resources:
       Type: String
       Value: !Ref LambdaAdapterLayerX86
 
-  LambdaAdapterLayerArm64VersionParameter:
-    Type: AWS::SSM::Parameter
-    DeletionPolicy: Retain
-    UpdateReplacePolicy: Retain
-    Properties:
-      Name: !Sub '/lambda-web-adapter/layer/x86_64/${CargoPkgVersion}'
-      Description: !Sub 'Layer ARN for the latest Lambda Web Adapter X86_64 Layer: ${CargoPkgVersion}'
-      Type: String
-      Value: !Ref LambdaAdapterLayerX86
+  # A per-version parameter (/lambda-web-adapter/layer/x86_64/<CargoPkgVersion>) used
+  # to live here. It was removed: because CloudFormation replaces a parameter when its
+  # Name changes, and UpdateReplacePolicy was Retain, every version bump orphaned the
+  # previous name. Deploying a version whose name had already been orphaned — after the
+  # v1.1.0 revert, or on any re-release — then failed with AlreadyExists and wedged
+  # every merge to main. Existing per-version parameters are retained, and the layer's
+  # Description still records the version, so `aws lambda list-layer-versions` maps a
+  # version to its layer ARN.
 
 Outputs:
   LambdaAdapterLayerX86Arn: