Explore bounded self-tuning with audit trail

[MichaelSchmidle]

Migrated from legacy Fizzy card #65 after Memrok work moved to GitHub Issues + milestones.

Goal

Explore self-tuning with bounded drift and audit trail.

Guardrails

• bounded drift only
• explicit audit trail of what changed and why
• easy manual override / reset
• no silent mutation of core ranking behavior without operator visibility
• evaluate against contamination / observer-effect pitfalls discovered during Memrok QA

Note

This is a later-stage capability, not the current priority.