test(cli): cover empty cors bucket segment

[overtrue]

Summary

This adds a focused regression test for the recent CORS bucket-path normalization fix. The new assertion covers local/, where the bucket segment becomes empty after trimming trailing slashes.

Problem

The recent fix in parse_bucket_path rejects bucket paths whose bucket segment normalizes to an empty string. The existing test only covered local///, so the simpler local/ input remained untested even though it exercises the same user-facing edge case.

Root Cause

The implementation was corrected, but the regression coverage did not include the shortest form of the empty normalized bucket path. That left the fix vulnerable to accidental changes in the parser contract.

Fix

I extended the existing parser error test in crates/cli/src/commands/cors.rs with an assertion that parse_bucket_path("local/") returns an error. The scope stays limited to the changed parser behavior and avoids unrelated command changes.

Validation

I ran:

• cargo test -p rustfs-cli test_parse_bucket_path_error
• cargo fmt --all --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo test --workspace

Note: this repository does not currently contain a make pre-commit target, so I ran the underlying CI-equivalent checks directly.