chore(configs): remove empty *ExperimentalConfig placeholders

[hallerite]

Summary

Deletes the four empty *ExperimentalConfig models (pass bodies) and their experimental fields from the inference, orchestrator, rl, and sft configs — 24 dead lines.

Repo-wide grep finds no reader of any .experimental attribute and no TOML setting one. Since the models are empty and BaseConfig uses extra="forbid", no key could ever be set under them; the only expressible usage was an empty [experimental] table. A future experimental namespace can be re-added together with its first real field.

Test plan

• uv run pytest tests/unit/test_configs.py — 114 passed

🤖 Generated with Claude Code

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Note

Low Risk
Schema-only cleanup with no runtime logic changes; the only user impact is TOMLs that still include [experimental], which will error on load.

Overview
Removes four no-op *ExperimentalConfig Pydantic models and their experimental fields from InferenceConfig, OrchestratorConfig, RLConfig, and SFTConfig.

Those blocks were empty (pass only) and unused in code or TOML; with extra="forbid", they could not hold future keys anyway. Breaking for configs that still declare an [experimental] table (including empty ones): validation will now reject that section, consistent with the earlier TrainerExperimentalConfig removal.

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