test(cli): cover object remove purge parser

[overtrue]

Summary

Recent --purge support added parser and execution coverage for rc rm, but the noun-first rc object remove entrypoint reuses the same RmArgs without dedicated parser coverage.

This change adds one focused parser test in crates/cli/src/commands/mod.rs to verify that rc object remove local/my-bucket/object.txt --purge is accepted and sets purge = true on the delegated remove args.

User impact

Without this test, a regression in the noun-first parser path could silently break object remove --purge while rm --purge kept passing. Users relying on the object-oriented command surface would lose the new flag behavior without a targeted signal in CI.

Validation

I first ran the focused parser test:

• cargo test cli_accepts_object_remove_with_purge_flag

The repository does not define make pre-commit, so that target cannot be run in this checkout. I ran the CI-equivalent checks from .github/workflows/ci.yml instead:

• cargo fmt --all --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo test --workspace