framework tools/git: pr-review body-required actions fail fast (codex suggestion on PR #1464)

request-changes and comment both validate their required body
immediately after argument parsing (rc 2, stderr, zero provider
contact). The repo-host-override suite's action-message expectation
updated to the new wording; suite green.

packages/mosaic/framework/tools/git/pr-review.sh

@@ -124,6 +124,13 @@ case "$ACTION" in
     *) usage_error "unknown action '$ACTION': approve, request-changes, comment" ;;
 esac
 
+# Body-required actions fail fast too (codex follow-up on PR #1464):
+# request-changes and comment both require a body; validate before any
+# provider contact.
+if [[ ( "$ACTION" == "request-changes" || "$ACTION" == "comment" ) && -z "$COMMENT" ]]; then
+    usage_error "comment required for $ACTION (-b/--body)"
+fi
+
 if [[ -n "$REPO_OVERRIDE" ]]; then
     # An explicit --repo is the whole point of a reviewer worktree whose origin
     # is nonstandard or missing (#867 convention, mirrored from pr-view.sh /