ci: activate mise before installing elixir so erl is on PATH

AI-Session-Id: d313020e-b6fc-439d-8bc0-7f32d644f376
AI-Tool: claude-code
AI-Model: unknown

Author: sanzmauro

.harness/pipeline.yaml

@@ -43,8 +43,8 @@ pipeline:
                       curl https://mise.run | sh
                       export PATH="$HOME/.local/bin:$PATH"
                       mise use --global erlang@<+matrix.otpVersion>
-                      mise use --global elixir@<+matrix.elixirVersion>
                       eval "$(mise activate bash)"
+                      mise use --global elixir@<+matrix.elixirVersion>
                       erl -eval 'erlang:display(erlang:system_info(otp_release)), halt().' -noshell
                       elixir --version
               - step: