Spiral Pool v2.7.0

• fix(celebration): stop the dashboard's on/off LED loop overwriting the RGB celebration (b7defcc)
• docs(changelog): record difficulty quantization fix under v2.7.0 (140de79)
• fix(stratum): quantize difficulty to wire precision so validation matches what miners are told (221189c)
• docs(changelog): record miner-classification and test fixes under v2.7.0 (b0f44fb)
• fix(shares): repair test-only WAL data race and race-mode heap-bound flake (447dd42)
• fix(stratum): recalibrate lottery difficulty, add NerdNOS class, add vardiff idle descent (3eed707)
• release: v2.7.0 — Spiral Citadel (02fb4e7)