Fix duplicate CLI shorthand flag registration

[benjibc]

Summary

• stop duplicate shorthand aliases from breaking CLI parser construction while preserving canonical prefixed flags
• reserve canonical option strings before registration so nested shorthand aliases cannot steal a later top-level flag
• add regression coverage for duplicate nested shorthands and top-level canonical flag preservation

Verification

• /var/folders/d4/gy675hy9779623fysvnk30zc0000gn/T/tmp.IE5N3GKtYD/venv/bin/pytest tests/test_cli_args.py -q
• /var/folders/d4/gy675hy9779623fysvnk30zc0000gn/T/tmp.IE5N3GKtYD/venv/bin/pytest tests/test_cli_create_rft.py -q -k test_cli_full_command_style_evaluator_and_dataset_flags

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Note

Medium Risk
Touches core CLI argument registration logic, so mistakes could break command parsing across multiple commands, but the change is small and covered by new regression tests.

Overview
Prevents add_args_from_callable_signature from registering conflicting option strings by reserving canonical flags up front and only adding alias/shorthand flags when they don’t collide with existing options or other canonical flags.

Adds regression tests ensuring duplicate nested shorthand flags are skipped and that a later top-level canonical flag cannot be “stolen” by an earlier nested shorthand alias. Separately, makes the Hugging Face adapter E2E test skip on common upstream network failures to reduce flakiness.

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