Tuning logic audit: 20 correctness/safety fixes, docs sync, 72 new tests - #433

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, actions/setup-node@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

'SDCARD_SUMMARY' is defined but never used. Allowed unused vars must match /^_/u

'mockConn' is assigned a value but never used. Allowed unused vars must match /^_/u

'timeout' is defined but never used. Allowed unused args must match /^_/u

'mockConn' is assigned a value but never used. Allowed unused vars must match /^_/u

'verAxes' is assigned a value but never used. Allowed unused vars must match /^_/u

'refAxes' is assigned a value but never used. Allowed unused vars must match /^_/u

'peakMatchTolerance' is defined but never used. Allowed unused vars must match /^_/u

'computeActivityRatio' is defined but never used. Allowed unused vars must match /^_/u

'DB_FLOOR_VALID' is assigned a value but never used. Allowed unused vars must match /^_/u