Config::forSampleRate — rate-scaled defaults for non-48 kHz deployments

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The library-side fix for the finding from #22: FilterSpec band edges and ServoConfig bandwidths are absolute Hz designed for 48 kHz, and running another rate with unscaled defaults silently costs ~32 dB. Users shouldn't have to know the scaling rule — now they don't.

API

• FilterSpec::scaledTo(rateHz) — band edges rescaled from the 48 kHz design rate (same L/T ⇒ identical normalized-frequency response).
• ServoConfig::scaledTo(rateHz) — the six Hz fields scale with the rate; hold times scale inversely (promotion gates wait the same number of loop time constants); frame-denominated thresholds and ppm limits are rate-invariant and stay put.
• Config::forSampleRate(rateHz) — composes both; the documented starting point for any non-48 kHz deployment.

Validation

• The 16 kHz quality suite now runs through the factory instead of hand-scaling, making it the behavioral regression test for this API: measured 136.6 / 122.0 / 114.3 / 106.5 dB — identical to 16 kHz quality suite: rate-scaled config, measured thresholds, gtest filter fix #22's hand-scaled numbers within 0.1 dB (this also validates the inverse hold-time scaling, which the hand-scaled original didn't apply).
• New fast unit test pins the scaling rule field by field (what scales, what must not).
• Full host suite 51/51 under -Werror; README's 16 kHz paragraph now points at the factory.

https://claude.ai/code/session_01HuAFfoeD5a5Xe5aGNA16M9

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Generated by Claude Code