Keep release.sh's DRY_RUN out of the release checks (#844)

make release hands scripts/release.sh DRY_RUN=false, and release.sh ran
make release-check with it still exported. test-sync-skills reads a
DRY_RUN of its own and accepts only unset, local or remote, so every
make release failed its checks before tagging. Run the checks without
it.

Author: robzolkos

scripts/release.sh

@@ -78,7 +78,10 @@ fi
 
 # --- Run pre-flight checks ---
 info "Running release checks"
-make release-check
+# DRY_RUN is this script's (true/false); the skill-sync tests read a DRY_RUN
+# of their own (unset, local or remote) and refuse "false". Keep it out of the
+# checks' environment.
+env -u DRY_RUN make release-check
 
 # --- Update stable release metadata ---
 if [[ "${PRERELEASE}" == "true" ]]; then