fix(ci): install Terraform 1.9.* in test + check-only jobs

The ci.yml workflow's test job runs test_adapter.py which includes
test_s3_instance_emits_valid_terraform — this test runs terraform
init+validate as a subprocess. Previously Terraform was not installed
in the CI job, causing FileNotFoundError. Now both the test and
check-only jobs install Terraform 1.9.* via the HashiCorp apt repo.

Reverted the skip-when-terraform-missing logic in the test — Terraform
is now always available in CI.

---ci---
project: acdl
phase: P59
milestone: v1.11
status: execute
---/ci---

.github/workflows/ci.yml

@@ -54,6 +54,12 @@ jobs:
         with:
           python-version: "3.12"
 
+      - name: Install Terraform 1.9.*
+        run: |
+          wget -qO- https://apt.releases.hashicorp.com/gpg | sudo gpg --dearmor -o /usr/share/keyrings/hashicorp.gpg
+          echo "deb [signed-by=/usr/share/keyrings/hashicorp.gpg] https://apt.releases.hashicorp.com $(lsb_release -cs) main" | sudo tee /etc/apt/sources.list.d/hashicorp.list
+          sudo apt-get update && sudo apt-get install -y terraform=1.9.*
+
       - name: Install test dependencies
         run: pip install -r requirements-test.txt
 
@@ -70,6 +76,12 @@ jobs:
         with:
           python-version: "3.12"
 
+      - name: Install Terraform 1.9.*
+        run: |
+          wget -qO- https://apt.releases.hashicorp.com/gpg | sudo gpg --dearmor -o /usr/share/keyrings/hashicorp.gpg
+          echo "deb [signed-by=/usr/share/keyrings/hashicorp.gpg] https://apt.releases.hashicorp.com $(lsb_release -cs) main" | sudo tee /etc/apt/sources.list.d/hashicorp.list
+          sudo apt-get update && sudo apt-get install -y terraform=1.9.*
+
       - name: Install runtime dependencies
         run: pip install jsonschema pyyaml boto3