feat(16-04): update Scheduler to dispatch by device_type via collectors

- Add collectors map[string]Collector field to Scheduler struct
- Register RouterOSCollector for "routeros" inside NewScheduler
- Replace direct PollDevice call with collector dispatch by dev.DeviceType
- Default empty DeviceType to "routeros" for backward compatibility
- Log error and exit device loop for unknown device types
- Circuit breaker logic unchanged

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

poller/internal/poller/scheduler.go

@@ -45,6 +45,10 @@ type Scheduler struct {
 	baseBackoff time.Duration
 	maxBackoff  time.Duration
 
+	// collectors maps device type name to its Collector implementation.
+	// "routeros" -> RouterOSCollector, "snmp" -> SNMPCollector (future).
+	collectors map[string]Collector
+
 	// activeDevices maps device ID to per-device state.
 	mu            sync.Mutex
 	activeDevices map[string]*deviceState
@@ -64,7 +68,10 @@ func NewScheduler(
 	baseBackoff time.Duration,
 	maxBackoff time.Duration,
 ) *Scheduler {
-	return &Scheduler{
+	// lockTTL gives the poll cycle time to complete: interval + connection timeout + 15s margin.
+	lockTTL := pollInterval + connTimeout + 15*time.Second
+
+	s := &Scheduler{
 		store:           store,
 		locker:          locker,
 		publisher:       publisher,
@@ -76,8 +83,14 @@ func NewScheduler(
 		maxFailures:     maxFailures,
 		baseBackoff:     baseBackoff,
 		maxBackoff:      maxBackoff,
+		collectors:      make(map[string]Collector),
 		activeDevices:   make(map[string]*deviceState),
 	}
+
+	// Register built-in collectors. Future device types (SNMP) register here.
+	s.collectors["routeros"] = NewRouterOSCollector(locker, credentialCache, connTimeout, cmdTimeout, lockTTL)
+
+	return s
 }
 
 // Run is the main scheduler loop. It:
@@ -175,16 +188,13 @@ func (s *Scheduler) reconcileDevices(ctx context.Context, wg *sync.WaitGroup) er
 }
 
 // runDeviceLoop is the per-device polling loop. It ticks at pollInterval and
-// calls PollDevice synchronously on each tick (not in a sub-goroutine, to avoid
+// dispatches to the appropriate Collector synchronously on each tick (not in a
-// unbounded goroutine growth if polls are slow).
+// sub-goroutine, to avoid unbounded goroutine growth if polls are slow).
 //
 // Circuit breaker: when consecutive failures exceed maxFailures, the device enters
 // exponential backoff. Poll ticks during backoff are skipped. On success, the
 // circuit breaker resets.
 func (s *Scheduler) runDeviceLoop(ctx context.Context, dev store.Device, ds *deviceState) {
-	// lockTTL gives the poll cycle time to complete: interval + connection timeout + 15s margin.
-	lockTTL := s.pollInterval + s.connTimeout + 15*time.Second
-
 	ticker := time.NewTicker(s.pollInterval)
 	defer ticker.Stop()
 
@@ -208,7 +218,22 @@ func (s *Scheduler) runDeviceLoop(ctx context.Context, dev store.Device, ds *dev
 				continue
 			}
 
-			err := PollDevice(ctx, dev, s.locker, s.publisher, s.credentialCache, s.connTimeout, s.cmdTimeout, lockTTL)
+			// Look up collector for this device type.
+			deviceType := dev.DeviceType
+			if deviceType == "" {
+				deviceType = "routeros" // backward compat default
+			}
+
+			collector, ok := s.collectors[deviceType]
+			if !ok {
+				slog.Error("no collector registered for device type",
+					"device_id", dev.ID,
+					"device_type", deviceType,
+				)
+				return // skip this device -- no collector available
+			}
+
+			err := collector.Collect(ctx, dev, s.publisher)
 
 			if err != nil {
 				ds.consecutiveFailures++