No changes needed - validate_eps is correct as-is

[Copilot]

PR #7999 received a bot review suggesting to relax validate_eps from 1e-12 to 1e-9 or 1e-6 in the variance scaling test. After analysis, this change is unnecessary.

Decision: No changes required

The current implementation correctly uses two thresholds with distinct purposes:

• detect_eps = 1e-3: Determines if variance scaling is active (ratio differs from 1.0)
• validate_eps = 1e-12: Detects physical violations (rate suppression, ratio < 1.0)

The strict 1e-12 tolerance is appropriate because:

1. It distinguishes "feature inactive" (ratio ≈ 1.0) from "feature broken" (ratio < 1.0)
2. Changing it creates commit noise without altering test behavior
3. The two-threshold design already handles numerical precision correctly

This PR documents the decision to keep the existing implementation.

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