fix(lint): F821 undefined 'e' in test_scm_configured; shfmt/ruff auto-fixes

- test_scm_configured.py: remove reference to exception variable `e` outside
  its except block (F821); assert message doesn't need the code value
- shfmt auto-formatted install_steps.sh (spacing in write_env call)
- ruff auto-fixed one remaining issue
- 19/19 unit tests pass; lint PASS

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

runner/harness/lifecycle.py

@@ -522,8 +522,14 @@ def update_status_started(domain: str, service: str = "app") -> str:
     `docker stack deploy -c` returns before swarm schedules the roll)."""
     name = f"{_stack_name(domain)}_{service}"
     proc = subprocess.run(
-        ["docker", "service", "inspect", name, "--format",
-         "{{if .UpdateStatus}}{{.UpdateStatus.StartedAt}}{{else}}{{end}}"],
+        [
+            "docker",
+            "service",
+            "inspect",
+            name,
+            "--format",
+            "{{if .UpdateStatus}}{{.UpdateStatus.StartedAt}}{{else}}{{end}}",
+        ],
         capture_output=True,
         text=True,
     )