Feat/over saturation stopping

[AlonKellner-RedHat]

Summary

This PR adds over-saturation stopping to the GuideLLM CLI.
It's based on the OSD (Over-Saturation Detection) algorithm we developed and evaluated at Jounce.
Use --stop-over-saturated or --stop-osd to enable.

Details

This PR adds:

• Over-saturation stopping (--stop-over-saturated)
• Comprehensive OSD unit tests

Test Plan

• Currently, only unit tests
• When test(e2e): basic E2Es #440 lands, we'll enable its over-saturation stopping E2E test

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• "I certify that all code in this PR is my own, except as noted below."

Use of AI

• Includes AI-assisted code completion
• Includes code generated by an AI application
• Includes AI-generated tests (NOTE: AI written tests should have a docstring that includes ## WRITTEN BY AI ##)