ci: run the Terraform isolation gate as a job in the CI workflow

.github/workflows/ci.yaml

@@ -71,6 +71,30 @@ jobs:
         env:
           GOVERNANCE_BASE: ${{ steps.governance-ref.outputs.base }}
 
+  terraform-isolation:
+    # Fails a pull request that changes `terraform/**` together with deployable
+    # application code (scripts/check-terraform-isolation.mjs). A merge that
+    # does both queues an HCP VCS run and a content release at the same time,
+    # and the two race for the workspace lock. The
+    # `terraform-isolation-override` label is the reviewed exception; it is
+    # read when the job runs, so re-run this workflow after labeling.
+    name: Terraform and application changes are isolated
+    if: github.event_name == 'pull_request'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          fetch-depth: 0
+      - uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020 # v7.0.0
+        with:
+          node-version: "24"
+      - name: Check changed files
+        env:
+          BASE_SHA: ${{ github.event.pull_request.base.sha }}
+          HEAD_SHA: ${{ github.event.pull_request.head.sha }}
+          TERRAFORM_ISOLATION_OVERRIDE: ${{ contains(github.event.pull_request.labels.*.name, 'terraform-isolation-override') }}
+        run: node scripts/check-terraform-isolation.mjs --base "${BASE_SHA}" --head "${HEAD_SHA}"
+
   visual-regression:
     name: Visual regression
     runs-on: ubuntu-latest

.github/workflows/terraform-isolation.yaml

@@ -1,35 +0,0 @@
-name: Terraform isolation
-
-# Fails a pull request that changes `terraform/**` together with deployable
-# application code (see scripts/check-terraform-isolation.mjs). A merge that
-# does both queues an HCP VCS run and a content release at the same time, and
-# the two race for the workspace lock.
-#
-# Runs on label events too, so adding or removing the
-# `terraform-isolation-override` label re-evaluates the gate without a push.
-
-on:
-  pull_request:
-    branches: [main, dev, staging]
-    types: [opened, synchronize, reopened, labeled, unlabeled]
-
-permissions:
-  contents: read
-
-jobs:
-  terraform-isolation:
-    name: Terraform and application changes are isolated
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-        with:
-          fetch-depth: 0
-      - uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020 # v7.0.0
-        with:
-          node-version: "24"
-      - name: Check changed files
-        env:
-          BASE_SHA: ${{ github.event.pull_request.base.sha }}
-          HEAD_SHA: ${{ github.event.pull_request.head.sha }}
-          TERRAFORM_ISOLATION_OVERRIDE: ${{ contains(github.event.pull_request.labels.*.name, 'terraform-isolation-override') }}
-        run: node scripts/check-terraform-isolation.mjs --base "${BASE_SHA}" --head "${HEAD_SHA}"

QUALITY_GATES.md

@@ -30,7 +30,7 @@ and synthesis. A task is not done until this is green.
 | Terraform isolation gate contract   | `npm run test:terraform-isolation` → `scripts/check-terraform-isolation.test.mjs`                           | `governance` + CI      | Changed-file classifier              |
 | Terraform formatting/validation     | `npm run test:terraform` → `scripts/terraform-validate.mjs`                                                 | `governance` + CI      | `terraform/live/dev`                 |
 | CDK build, tests, synthesis         | `npm run test:infra`                                                                                        | `governance` + CI      | `infra/cdk/**`, both synth modes     |
-| Terraform/app change isolation      | `.github/workflows/terraform-isolation.yaml` → `scripts/check-terraform-isolation.mjs`                      | CI (PR)                | Changed files of the PR              |
+| Terraform/app change isolation      | `ci.yaml` job `terraform-isolation` → `scripts/check-terraform-isolation.mjs`                               | CI (PR)                | Changed files of the PR              |
 
 ## No-false-pass guarantees
 
@@ -49,9 +49,10 @@ and synthesis. A task is not done until this is green.
   against synthetic plan JSON. Real import and controlled-update plans from HCP
   are migration evidence reviewed by a human before an approved apply
   (`terraform/README.md`).
-- **The isolation gate re-evaluates on label changes** — the
+- **The isolation gate reads the override when it runs** — the
   `terraform-isolation-override` label is the only way to merge a mixed
-  Terraform/application PR, and the gate logs the override on the run.
+  Terraform/application PR, the gate logs the override on the run, and the
+  workflow must be re-run after the label is added or removed.
 
 ## Where the gates run
 
@@ -62,10 +63,9 @@ and synthesis. A task is not done until this is green.
   format/lint/build/tests, **and** a repo-owned `governance` job runs
   `npm run verify` (with Terraform 1.16.0 installed) so the maintainability
   ratchets and repository gates are guaranteed from this repository regardless
-  of the reusable workflow.
-- **CI ([`.github/workflows/terraform-isolation.yaml`](.github/workflows/terraform-isolation.yaml)):**
-  on every PR (including label events), fails when `terraform/**` and
-  application code change together.
+  of the reusable workflow. On pull requests the same workflow's
+  `terraform-isolation` job fails when `terraform/**` and application code
+  change together.
 
 ## Toolchain pin
 

README.md

@@ -135,8 +135,8 @@ commitlint enforces conventional commit messages. Run `npx tsc --noEmit` (or
   a green CI run and an approving review from a code owner
   (`@Sea-Haven-Industries/internal-dev`); new pushes dismiss stale approvals.
   Merged branches are deleted automatically.
-- A PR that changes `terraform/**` may not also change application code
-  (`.github/workflows/terraform-isolation.yaml`); ship Terraform in its own PR.
+- A PR that changes `terraform/**` may not also change application code (the
+  `terraform-isolation` CI job); ship Terraform in its own PR.
 - Promotion flow: `feature/* → dev` (deployed to `dev.seahaven.com` through the
   **Deploy dev content** workflow while the Terraform adoption is in progress)
   `→ main` (production promotion — no prod environment exists yet).
@@ -156,10 +156,10 @@ No stored AWS keys — OIDC only. Infrastructure and content deploy separately:
   [`AGENTS.md`](AGENTS.md), [`QUALITY_GATES.md`](QUALITY_GATES.md),
   [`ARCHITECTURE_AND_CODE_QUALITY.md`](ARCHITECTURE_AND_CODE_QUALITY.md), and
   [`REVIEW_AND_PR_FRAMEWORK.md`](REVIEW_AND_PR_FRAMEWORK.md).
-- **Terraform isolation**
-  ([`.github/workflows/terraform-isolation.yaml`](.github/workflows/terraform-isolation.yaml))
-  — fails a PR that mixes `terraform/**` with application code, so a Terraform
-  merge never races a content release for the HCP workspace.
+- **Terraform isolation** (the `terraform-isolation` job in
+  [`.github/workflows/ci.yaml`](.github/workflows/ci.yaml)) — fails a PR that
+  mixes `terraform/**` with application code, so a Terraform merge never races
+  a content release for the HCP workspace.
 - **Dev content** ([`.github/workflows/deploy.yml`](.github/workflows/deploy.yml))
   — `workflow_dispatch` on `dev` only while the Terraform adoption is in
   progress. Runs `npm run verify`, assumes `githubdeploy-shoc-frontend-new-dev`,

infra/cdk/README.md

@@ -36,8 +36,7 @@ infra/cdk/
   test/frontend-stack.test.mjs        template assertions for both modes
 scripts/deploy-web.sh                 build SPA -> s3 sync -> CloudFront invalidation
 .github/workflows/
-  ci.yaml                             quality gates (lint / build / test / governance)
-  terraform-isolation.yaml            PRs may not mix terraform/** with app code
+  ci.yaml                             quality gates (lint / build / test / governance / terraform isolation)
   deploy.yml                          dev content publish (workflow_dispatch on dev)
   deploy-staging.yml                  standalone staging deploy (push to staging)
 ```

terraform/README.md

@@ -217,11 +217,12 @@ the labels. Push-to-`dev` releases return behind the repository variable
 ## Operational rules
 
 - **Terraform-only PRs.** A PR that changes `terraform/**` may not change
-  deployable application code. `.github/workflows/terraform-isolation.yaml`
-  enforces this; documentation and the `scripts/*terraform*` tooling are
-  allowed alongside. A reviewer may add the `terraform-isolation-override`
-  label for the rare change that must introduce Terraform variables together
-  with the workflow that consumes them (PR A and PR C). The label is the
+  deployable application code. The `terraform-isolation` job in
+  `.github/workflows/ci.yaml` enforces this; documentation and the
+  `scripts/*terraform*` tooling are allowed alongside. A reviewer may add the
+  `terraform-isolation-override` label for the rare change that must introduce
+  Terraform variables together with the workflow that consumes them (PR A and
+  PR C), then re-run the workflow so the job reads the label. The label is the
   approval record. The override is temporary: a follow-up PR after PR C
   removes the label path from the checker and workflow so the gate has no
   exception.