Normalize run config payload for determinism

[WhatsYourWhy]

Motivation

• Ensure run metadata and manifest/ledger hashes are deterministic across different output directories by removing non-semantic output_dir from the serialized run config payload.

Description

• Drop output_dir from the run config payload in run() by adding config_payload.pop("output_dir", None) to determinant/run.py so manifests do not incorporate environment-specific paths.

Testing

• Ran pytest -q, which failed during collection with ModuleNotFoundError: No module named 'determinant' (tests were not able to execute to completion).

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Codex Task