ci(action_tests): install terraform-docs, unskip its action test

The terraform-docs action's pre-commit hook shells out to the
`terraform-docs` binary. Without it on PATH inside the test sandbox,
the action exits with "terraform-docs not found" and the assertion on
the README-staging error never fires.

Mirrors the existing pattern for uv: install the binary in the
Action Tests composite step (ubuntu-latest only, which matches the
job's runs-on). With the binary available, the test can drop its
skipTestIf guard and actually exercise the monorepo-aware behavior.

Author: claude

.github/actions/action_tests/action.yaml

@@ -36,6 +36,21 @@ runs:
       with:
         version: 0.7.8
 
+    # The terraform-docs action's pre-commit hook shells out to
+    # `terraform-docs`, so the binary needs to be on PATH inside the action
+    # sandbox. There is no maintained setup-terraform-docs action, so install
+    # the release tarball directly. Action Tests only run on ubuntu-latest.
+    - name: Setup terraform-docs
+      run: |
+        version=0.16.0
+        tmp=$(mktemp -d)
+        curl -sSLo "$tmp/terraform-docs.tgz" \
+          "https://github.com/terraform-docs/terraform-docs/releases/download/v${version}/terraform-docs-v${version}-linux-amd64.tar.gz"
+        tar -xzf "$tmp/terraform-docs.tgz" -C "$tmp"
+        sudo install -m 0755 "$tmp/terraform-docs" /usr/local/bin/terraform-docs
+        terraform-docs --version
+      shell: bash
+
     - name: Specify defaults
       run: |
         echo "CLI_PATH=${{ inputs.cli-path }}" >> "$GITHUB_ENV"

actions/terraform-docs/terraform_docs.test.ts

@@ -44,15 +44,9 @@ const testCallback = async (driver: TrunkActionDriver) => {
   expect(commitError?.message).toContain("Please stage any README changes before committing.");
 };
 
-// NOTE: Skipped by default. Running this test requires `terraform-docs` on
-// PATH inside the action sandbox; the action's plugin.yaml does not declare a
-// tool dependency, so CI would need a setup step (similar to the uv setup in
-// .github/actions/action_tests/action.yaml) to install terraform-docs before
-// the jest run. Drop `skipTestIf` once that is in place.
 actionRunTest({
   actionName: "terraform-docs",
   syncGitHooks: true,
   preCheck,
   testCallback,
-  skipTestIf: () => true,
 });