feat(iam): allow frontend HCP apply to own release pointer and invalidation (PLAT-188)

Plan and apply roles can read .release/current; apply can PutObject that key and CreateInvalidation on the exact distribution.

README.md

@@ -439,7 +439,9 @@ job:
    existing site resources only after a no-replacement plan. Apply-role writes
    are limited to ordinary tags, `PutRolePolicy` on the exact deploy role,
    `PutBucketPolicy` on the exact bucket, `UpdateDistribution` on the exact
-   distribution, `UpdateFunction` and `PublishFunction` on the exact CloudFront
+   distribution, `CreateInvalidation`/`GetInvalidation` on the exact
+   distribution, `GetObject`/`PutObject` on `.release/current`,
+   `UpdateFunction` and `PublishFunction` on the exact CloudFront
    function, and A/AAAA changes for the exact site name with
    CREATE/DELETE/UPSERT conditions.
 5. For a future tf-poc, first provision and inventory the site outside these
@@ -456,7 +458,9 @@ The apply roles explicitly deny role lifecycle/trust/boundary/managed-policy
 changes, `PassRole`, secret and parameter reads, CloudFront/S3 create and
 delete (including OAC mutation), and deletion of inline role or bucket
 policies. `UpdateDistribution` is allowed on the exact pinned distribution ARN.
-`UpdateFunction` and `PublishFunction` are allowed on the exact pinned function
+`CreateInvalidation` and `GetInvalidation` are allowed on that same ARN so the
+Terraform invalidation action can run. `GetObject`/`PutObject` on
+`.release/current` lets Terraform own the release pointer. `UpdateFunction` and `PublishFunction` are allowed on the exact pinned function
 ARN so Phase 2 ownership tags can apply; create, delete, and OAC updates stay
 denied. IAM does not expose a condition key for an inline policy name, so
 `PutRolePolicy` is constrained to the exact target-role ARN and requires the

lib/terraform-substrate/shoc-frontend-resources.ts

@@ -113,6 +113,12 @@ const frontendReadPolicy = (
         ],
         Resource: siteBucketArn,
       },
+      {
+        Sid: "ReadReleasePointerObject",
+        Effect: "Allow",
+        Action: ["s3:GetObject", "s3:GetObjectVersion"],
+        Resource: `${siteBucketArn}/.release/current`,
+      },
       {
         Sid: "ReadExactCloudFrontResources",
         Effect: "Allow",
@@ -343,6 +349,18 @@ const frontendApplyPolicy = (
       Action: ["cloudfront:UpdateFunction", "cloudfront:PublishFunction"],
       Resource: functionArn(environment.functionName),
     },
+    {
+      Sid: "InvalidateExactDistribution",
+      Effect: "Allow",
+      Action: ["cloudfront:CreateInvalidation", "cloudfront:GetInvalidation"],
+      Resource: distributionArn(environment.distributionId),
+    },
+    {
+      Sid: "WriteReleasePointerObject",
+      Effect: "Allow",
+      Action: ["s3:GetObject", "s3:GetObjectVersion", "s3:PutObject"],
+      Resource: `${bucketArn(environment.bucketName)}/.release/current`,
+    },
     {
       Sid: "ReplaceExactDeployInlinePolicy",
       Effect: "Allow",