ax(mining): replace prose comment on NewManagerForSimulation with usage example

AX Principle 2: comments must show HOW with real values, not restate what
the type signature already says. Replaced description prose with a concrete
call pattern showing ctx + Config.

Co-Authored-By: Charon <charon@lethean.io>

pkg/mining/manager.go

@@ -77,8 +77,8 @@ func NewManager() *Manager {
 	return m
 }
 
-// NewManagerForSimulation creates a manager for simulation mode.
-// It skips autostarting real miners and config sync, suitable for UI testing.
+// manager := mining.NewManagerForSimulation()
+// manager.StartMiner(ctx, "xmrig", &mining.Config{Algo: "rx/0"})
 func NewManagerForSimulation() *Manager {
 	m := &Manager{
 		miners:    make(map[string]Miner),