Implement working motor init command using limit-switch homing

Added `motor init [up|down] [timeout]` that homes the altitude axis by
slewing to a mechanical limit. The firmware detects the limit switch and
performs an automatic home to position 0 (optics toward ground).

Validated procedure:
1. Slew up briefly (90° 0.4 for 5s) to move away from the bottom limit
2. `motor init down 40` — slew 270° until bottom limit triggers auto-home
3. Axis remains fully operational after homing

The firmware drops the WebSocket connection when the home sequence starts
(normal behavior). After reconnecting, the axis works normally.

Note: API still returns NEED_RESET (-14520) because absolute positioning
requires astro calibration (plate solving). The mechanical home only
provides physical position 0, not sky coordinates.

💘 Generated with Crush

Assisted-by: Crush:glm-5.2

dwarfctl/cmd/dwarfctl/main.go

@@ -397,6 +397,28 @@ func cmdMotor() *cobra.Command {
 				fmt.Printf("motor %d: id=%d code=%d position=%.2f\n", id, pos.GetId(), pos.GetCode(), pos.GetPosition())
 			},
 		},
+		&cobra.Command{
+			Use:   "init [up|down] [timeout]",
+			Short: "Home altitude axis by slewing to a mechanical limit (safe, daytime)",
+			Args:  cobra.MaximumNArgs(2),
+			Run: func(_ *cobra.Command, args []string) {
+				dir := 90.0 // default: up
+				if len(args) > 0 && args[0] == "down" {
+					dir = 270.0
+				}
+				timeout := 30
+				if len(args) > 1 {
+					timeout = int(parseInt32(args[1]))
+				}
+				scope, cleanup := dial()
+				defer cleanup()
+				dirStr := "up (toward sky)"
+				if dir == 270 { dirStr = "down (toward ground)" }
+				fmt.Printf("Initializing: slewing %s at 0.5 until limit (max %ds)...\n", dirStr, timeout)
+				must(scope.MotorInit(dir, timeout))
+				fmt.Println("Init complete.")
+			},
+		},
 	)
 	return c
 }