test(cli): cover rm purge dry-run

[overtrue]

Summary

This PR adds coverage for a recent rm --purge path that was still untested: running the command with --dry-run against a versioned object. Without this test, the purge feature only had assertions for real deletes, not for the safety path that should avoid both permanent deletion and delete-marker creation.

The branch also adds a minimal root Makefile with a pre-commit target because this repository did not expose make pre-commit, while the documented local validation steps already existed as standalone cargo commands. The new target simply wraps the existing required checks.

Root Cause

The recent purge work added permanent-delete behavior, but the dry-run interaction lived on a separate execution path and did not have focused regression coverage. That left a gap where a future change could accidentally route dry-run purge requests into the destructive path without a targeted test failing.

Fix

The new integration test enables versioning, uploads a single object, runs rc rm --purge --dry-run --json, and then verifies that the object still has exactly one non-delete-marker version. This keeps the scope on the changed rm purge area and exercises the user-visible behavior directly.

Validation

• cargo test --features integration --test integration option_behavior_operations::test_rm_purge_dry_run_does_not_delete_versioned_object -- --exact --nocapture
• make pre-commit