fix: time-division multiplexing for 2-anchor collision avoidance

Each anchor only runs DW1000Ranging during its 50ms time slot.
Anchor 0 responds in even slots, anchor 1 in odd slots.
Prevents RF collisions that caused wild range readings.

esp32/uwb_anchor/src/main.cpp

@@ -195,8 +195,21 @@ void setup(void) {
 
 /* ── Loop ───────────────────────────────────────────────────────── */
 
+/*
+ * Time-division multiplexing: 2 anchors share the same channel.
+ * Each anchor only responds during its time slot to avoid RF collisions.
+ * Slot duration = 50ms → each anchor gets 10 Hz effective rate.
+ * Anchor 0 responds during even slots, anchor 1 during odd slots.
+ */
+#define SLOT_MS  50
+#define NUM_ANCHORS_TOTAL  2
+
 void loop(void) {
     serial_poll();
     espnow_process();
-    DW1000Ranging.loop();
+
+    uint32_t slot = (millis() / SLOT_MS) % NUM_ANCHORS_TOTAL;
+    if (slot == ANCHOR_ID) {
+        DW1000Ranging.loop();
+    }
 }