wshub: persist calibration alongside sources; add config reload

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Common/Client/go/wshub/hub.go

@@ -239,6 +239,10 @@ type Hub struct {
 
 	sm *SourceManager // set after construction; used for WS-initiated source changes
 
+	// cal holds the per-signal calibration table.  It is metadata only: the
+	// rings, the history and the trigger comparator all keep raw samples.
+	cal *calTable
+
 	// Ring buffers for hi-res zoom data.
 	// ringsMu protects the map structure; each sigRing has its own RWMutex for data.
 	ringsMu sync.RWMutex
@@ -270,6 +274,7 @@ func NewHub() *Hub {
 		rings:       make(map[string]*sigRing),
 		statsMap:    make(map[string]*SourceStat),
 		trigger:     newTriggerEngine(),
+		cal:         newCalTable(),
 	}
 }