fix(ci): use || to capture exit code before set -e kills the script

GitHub Actions run blocks use set -e; the previous EXIT=$? was never
reached because mix test --cover exited 3 first. Use || to capture it.

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

Author: hyperpolymath

.github/workflows/elixir-ci.yml

@@ -37,11 +37,10 @@ jobs:
 
       - name: Run tests
         run: |
-          mix test --cover
-          EXIT=$?
+          mix test --cover || EXIT=$?
           # Exit 3 = coverage threshold not met; acceptable while integration
           # tests are excluded (no WASM binary in CI). Tests still fail on 1/2.
-          [ $EXIT -eq 0 ] || [ $EXIT -eq 3 ] || exit $EXIT
+          [ "${EXIT:-0}" -eq 3 ] || exit "${EXIT:-0}"
       
       - name: Security check
         run: mix deps.audit || true