Fusion engine

ImpactFusion runs a fan-in TaskGroup across every active impact sensor, holds a sliding window for consensus, applies sensitivity remapping, and then publishes one Reaction.impact. The rearm gate is the difference between an app that yells once when you smack it and an app that yells four times because four sensors agreed.

Individual sensor impacts feed into ImpactFusion, which enforces two additional constraints before publishing a Reaction.impact onto the bus: consensus (enough sensors must agree within a time window) and rearm (minimum gap between consecutive responses). Before publishing, the sensitivity gate. an intensityGate closure set by the orchestrator. maps raw fused intensity through the user's sensitivity band and drops impacts that fall below the floor.

      ImpactFusion.ingest() -- one call per SensorImpact

The default consensusRequired = 1 means any single sensor can trigger a response. Set it to 2 and both the accelerometer and microphone have to agree within 150 ms before anything fires. eliminates most false positives at the cost of some missed detections on very clean impacts. The engine clamps consensusRequired to the active source count at runtime, so "require 2" against a single connected sensor still emits.

Parameter	Default	Effect
fusionWindow	150 ms	Time window within which multiple sensors must all fire to count as consensus
consensusRequired	1	Minimum distinct sensor sources in window before firing (clamped to active count)
rearmDuration	user debounce	Minimum gap between consecutive fused impacts; set from SettingsStore.debounce