fix(ultrabeam): hold a commanded pattern over a remote link until confirmed

Changing Normal/180/bi over a remote connection reverted to the old pattern
after ~4s: the fixed 4s optimistic window expired while the motors were still
flipping the elements, and the lagging remote status poll then overrode the UI.
Hold the commanded direction while the motors are moving, then a short grace
window after they stop for the confirmation poll to land (SteppIR already used
a generous 45s hold, which is why only Ultrabeam-remote hit this).

internal/ultrabeam/ultrabeam.go

@@ -23,6 +23,12 @@ const (
 	ubReadTimeout    = 4 * time.Second  // was 1s — too tight for a remote link
 	ubKeepAlive      = 15 * time.Second // OS-level TCP keepalive
 	ubMaxPollTimeout = 3                // consecutive read timeouts tolerated before reconnecting
+	// How long a just-commanded direction is trusted AFTER the motors have stopped
+	// but before the antenna's status confirms it. The timer is held off entirely
+	// while the motors are still moving, so this is only the grace period for the
+	// confirmation poll to arrive once the elements have settled — generous, because
+	// over a remote link that poll lags by several seconds.
+	ubPendingDirGrace = 8 * time.Second
 )
 
 // Protocol constants
@@ -221,12 +227,30 @@ func (c *Client) pollLoop() {
 			}
 
 			c.statusMu.Lock()
-			// Keep a just-commanded direction until the antenna reports it.
+			// Keep a just-commanded direction until the antenna actually reports it.
+			// Over a remote link the confirmation arrives several seconds after the
+			// command — the motors flip the elements first — so the old fixed 4 s
+			// timeout expired WHILE the change was still in flight, and the stale poll
+			// reverted the UI to the old pattern even though the antenna was on its way
+			// to the new one. Now: while the motors are still moving the change is in
+			// progress, so hold the commanded pattern and keep resetting the timer;
+			// only once the motors have stopped does the short grace window run, giving
+			// the confirmation poll time to land. The poll only wins if the motors are
+			// idle AND the antenna still reports a different pattern past that window —
+			// i.e. the command genuinely did not take.
 			if c.pendingDirSet {
-				if time.Since(c.pendingDirAt) > 4*time.Second || status.Direction == c.pendingDir {
-					c.pendingDirSet = false
-				} else {
-					status.Direction = c.pendingDir
+				if status.MotorsMoving != 0 {
+					c.pendingDirAt = time.Now() // still repositioning — don't start the grace timer
+				}
+				switch {
+				case status.Direction == c.pendingDir:
+					c.pendingDirSet = false // confirmed by the antenna
+				case time.Since(c.pendingDirAt) > ubPendingDirGrace:
+					c.pendingDirSet = false // motors idle, still unconfirmed → accept the poll
+					log.Printf("Ultrabeam: antenna never confirmed direction %d (reports %d) — dropping the hold",
+						c.pendingDir, status.Direction)
+				default:
+					status.Direction = c.pendingDir // still changing, or within the grace window
 				}
 			}
 			c.lastStatus = status