test(cli): cover object remove purge behavior

[overtrue]

Summary

This change adds focused coverage for the noun-first rc object remove entrypoint in the recent versioned purge flow.

The existing integration test for force-delete behavior only exercised rc rm --purge. That covered the shared implementation, but it left the newer object remove command path unverified end to end. If that alias stopped wiring RmArgs through correctly, users invoking the documented noun-first command could silently lose permanent-delete behavior while the legacy path still passed.

This patch keeps the scope narrow by updating the existing versioned-object purge integration test to perform the purge step through rc object remove --purge --json. The surrounding assertions stay the same, so the test still proves that a normal delete leaves a delete marker while the purge path removes all versions.

Validation

I could not run make pre-commit because this repository does not contain a Makefile or pre-commit target. I ran the documented checks directly instead:

• cargo fmt --all --check
• cargo clippy --workspace -- -D warnings
• cargo test --workspace
• cargo test -p rustfs-cli --features integration --test integration version_operations::test_rm_purge_permanently_deletes_versioned_object -- --exact --nocapture

The targeted integration test passes in this environment and skips cleanly when S3 test credentials are not configured.