warn if large datasets + force 1 run

[xzrderek]

Note

Adds a best-effort warning for large JSONL datasets in ep create rft and enforces --ep-num-runs 1 for local/Docker pytest runs.

• CLI - create RFT (eval_protocol/cli_commands/create_rft.py):
  • Adds _warn_if_large_dataset() to print a warning when the provided dataset_jsonl exceeds a row threshold (default 200).
  • Invokes the warning (with path resolution) before local validation when --dataset-jsonl is used.
• Local test runner (eval_protocol/cli_commands/local_test.py):
  • Forces single run by adding --ep-num-runs 1 to pytest invocations on host and in Docker.
• Tests (tests/test_cli_create_rft.py):
  • Adds tests covering the large-dataset warning behavior (silent when small, warns when large).

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