🧪 Add trl.experimental Submodule

[August-murr]

Adds a minimal trl.experimental namespace for fast iteration on unstable features plus pytest tooling so experimental tests never block unrelated PRs.

Key Changes

• New package: trl/experimental/__init__.py with import warning (silence via TRL_EXPERIMENTAL_SILENCE=1).
• Docs: docs/source/experimental.md + toctree entry; simplified promotion path & FAQ.
• README: New "Experimental Namespace" section.
• Testing infra: @pytest.mark.experimental + custom flag --run-experimental in tests/conftest.py (experimental tests skipped by default).
• Smoke test: tests/test_experimental_namespace.py (marked experimental) ensures namespace imports.

Usage

Default (skip experimental):

pytest

Run all including experimental:

pytest --run-experimental

Only experimental tests:

pytest -m experimental --run-experimental

Silence import warning:

export TRL_EXPERIMENTAL_SILENCE=1

[qgallouedec]

🧪🧪🧪

[HuggingFaceDocBuilderDev]

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