Adaptive difficulty engine (per-employee scenario ladder)

[jusso-dev]

Why

Hoxhunt's core differentiator. Templates have a difficulty int but no engine.

Scope

• Engine selects next template per employee from a difficulty curve based on prior performance + recency.
• Adaptive intervals (don't re-test same template within N months.
• Per-employee training delta drives the difficulty step.

Acceptance

• Two employees with different histories get different templates from the same campaign config.
• Engine outputs a stable, auditable rationale per assignment.
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