test(cli): cover noun-first stat and share help

[overtrue]

Summary

This change adds focused contract coverage for the noun-first object commands introduced in the recent bucket/object command-group work. The existing help contract suite already covered rc object copy and rc object show, but it did not assert discoverability for delegated rc object stat and rc object share subcommands, and there was no direct parser test for rc object stat.

Root cause

The noun-first command groups were added with thin delegation to the existing command implementations, but only a subset of those delegated paths received fast parser/help coverage. That left a gap where regressions in rc object stat or rc object share discoverability could slip through even though those commands are part of the user-facing noun-first surface.

Fix

The help contract test matrix now includes rc object stat --help and rc object share --help, asserting the usage shape and their key option tokens. The CLI unit tests also now parse rc object stat local/my-bucket/report.json and verify it routes to ObjectCommands::Stat with the expected path.

Validation

I first ran focused tests for the touched areas:

• cargo test -p rustfs-cli --test help_contract nested_subcommand_help_contract
• cargo test -p rustfs-cli cli_accepts_object_stat_subcommand

I then ran the repository's documented checks:

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

I also attempted make pre-commit because the automation requested it, but this repository currently has no Makefile or pre-commit target, so that exact command cannot be executed in this checkout.