feat(transfer): add get and put compatibility aliases

[cxymds]

Summary

• add top-level rc get and rc put compatibility commands
• route both commands through the existing cp planner and execution path
• enforce download/upload direction before any remote request
• keep non-existent local paths containing / from being misclassified as remote aliases
• add parser, direction, exit-code/equivalence, help-contract, and documentation coverage

Why

RustFS CLI has the canonical copy implementation, but the mc-compatible get and put entry points from rustfs/backlog#1382 were still missing. Thin direction-aware wrappers provide compatibility without duplicating transfer behavior.

User impact

rc get accepts exactly one remote source and a local target. rc put accepts one or more local sources and a remote target. Retry, progress, errors, fidelity options, and output remain identical to rc cp because all commands use the same implementation.

BREAKING change assessment

BREAKING: no. These are new compatibility entry points and do not change the existing rc cp interface or execution behavior. The marker is included because this PR updates protected command reference documentation.

Validation

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

Closes rustfs/backlog#1485
Refs rustfs/backlog#1382