Treat a Railway environment's STAGED status as a prompt to inspect the patch

General lesson: Treat a Railway environment's STAGED status as a prompt to inspect the patch, not proof that there is a change to commit. An empty staged record can coexist with STAGED while environmentPatchCommitStaged(skipDeploys:true) rejects it as BAD_USER_INPUT / “No patch to apply.” For automation, fail on any nonempty pre-existing patch; if the patch is exactly empty, merge the intended update rather than replacing staged state, inspect the resulting full staged keyset, and commit with skipDeploys only if it matches the intended diff. This applies to Railway's environment-patch API; it is not a guarantee that every empty STAGED record can be merged successfully, nor a substitute for checking deployment state after commit.