ci(hypatia-scan): fix unresolvable setup-beam version pins

elixir 1.19.4 / otp 28.3 are not in the setup-beam version index, so
the "Setup Elixir" step failed fast on every run, making the Hypatia
dogfooding job red estate-wide regardless of PR content. Pin to
currently-published loose major/minor versions instead.

https://claude.ai/code/session_01GTo7dz32ZgxuHXefv8BGqn

Author: claude

.github/workflows/hypatia-scan.yml

@@ -28,8 +28,14 @@ jobs:
       - name: Setup Elixir for Hypatia scanner
         uses: erlef/setup-beam@fc68ffb90438ef2936bbb3251622353b3dcb2f93 # v1.24.0
         with:
-          elixir-version: '1.19.4'
-          otp-version: '28.3'
+          # Pinned to currently-published, setup-beam-resolvable versions.
+          # The previous pins (elixir 1.19.4 / otp 28.3) do not exist in the
+          # setup-beam index, so this step failed fast on every run and made
+          # the dogfooding job red estate-wide regardless of PR content.
+          # Major/minor (loose) so patch availability cannot re-break it.
+          # Bump deliberately to whatever Hypatia's scanner actually requires.
+          elixir-version: '1.18'
+          otp-version: '27'
 
       - name: Clone Hypatia
         run: |