fix: make agent callback logging opt-in for CLIs

[DavidJBianco]

Motivation

• The CLIs previously wired preprocess_messages_logging and postprocess_messages_logging by default, causing prompt/result previews to be persisted to fixed local files and creating a local information-leak risk.
• The intent is to preserve the debugging callbacks while preventing unintentional leakage during normal runs by making disk logging an explicit opt-in.

Description

• Added a --debug-agents CLI flag to peak_assistant/data_assistant/__main__.py, peak_assistant/planning_assistant/__main__.py, and peak_assistant/hypothesis_assistant/hypothesis_refiner_cli.py to opt in to debug callback logging.
• Introduced a debug_agents_opts dict in each CLI that is populated only when --debug-agents is set and passed into the agent invocation via **debug_agents_opts.
• Removed the unconditional passing of msg_preprocess_callback=preprocess_messages_logging and msg_postprocess_callback=postprocess_messages_logging so callbacks are no longer enabled by default.
• Preserved the existing preprocess_messages_logging and postprocess_messages_logging implementations so debug behavior remains available when explicitly requested.

Testing

• Ran a targeted search to confirm the new --debug-agents flag and that callbacks are no longer wired by default with rg -n "msg_preprocess_callback=preprocess_messages_logging|msg_postprocess_callback=postprocess_messages_logging|--debug-agents" which returned the updated CLI locations.
• Compiled the modified CLI modules with python -m compileall peak_assistant/data_assistant/__main__.py peak_assistant/planning_assistant/__main__.py peak_assistant/hypothesis_assistant/hypothesis_refiner_cli.py and the compilation succeeded.

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Codex Task

[DavidJBianco]

Merged into dev via #87 (batch-c-logging-opt-in, commit 2597449).