fix: unset stale GH_HOST when configuring gh for github.com (#24222)

* Initial plan

* fix: unset stale GH_HOST when github_host is github.com

Agent-Logs-Url: https://github.com/github/gh-aw/sessions/30a6422b-97fb-4c86-bb2a-187e682fd2d2

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

* fix: omit stale GH_HOST value from log and clear rather than set in GITHUB_ENV

Agent-Logs-Url: https://github.com/github/gh-aw/sessions/f7fa60de-4903-4101-bfa5-3211d8b0c0e0

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
Co-authored-by: Peli de Halleux <pelikhan@users.noreply.github.com>

Author: Copilot

actions/setup/sh/configure_gh_for_ghe.sh

@@ -75,6 +75,14 @@ main() {
       fi
     fi
     echo "Using public GitHub (github.com) - no additional gh configuration needed"
+    # Clear any stale GH_HOST to prevent gh CLI mismatches
+    if [ -n "${GH_HOST:-}" ] && [ "${GH_HOST}" != "github.com" ]; then
+      echo "Clearing stale GH_HOST" >&2
+      unset GH_HOST
+      if [ -n "${GITHUB_ENV:-}" ]; then
+        echo "GH_HOST=" >> "${GITHUB_ENV}"
+      fi
+    fi
     return 0
   fi