test(event): cover shorthand normalization deduplication

[overtrue]

Summary

This change closes a regression-test gap in the event notification parser.

The recent event shorthand normalization fix correctly maps aliases such as put, get, and delete to their canonical S3 event names before notification rules are persisted. That behavior was already covered for plain shorthand inputs, but there was still no test proving that shorthand aliases collapse with already-canonical event names into a single persisted value.

Without this regression test, a future refactor could accidentally reintroduce duplicate notification events whenever users mix shorthand flags and canonical event names in the same command invocation.

Root cause

The changed code path normalizes event names first and only then sorts and deduplicates them. The existing tests did not exercise the specific case where shorthand inputs and canonical S3 event names should normalize to the same final string before deduplication.

Fix

Add a focused unit test in crates/cli/src/commands/event.rs that covers mixed shorthand and canonical event inputs and asserts that the parser returns a deduplicated canonical event list.

Validation

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

[overtrue]

Superseded by #69, which now carries the broadened mixed shorthand/canonical event dedup coverage from this run.