feat: make VT100 console opt-in, off by default

The Box-3 display supersedes the VT100 serial UI, and the UI was
actively harmful to the link: each full refresh writes ~600 bytes
through the blocking Serial at 115200 baud (~40-50 ms) from the
same core 0 task as Link_Process, degrading the STATE rate from
20 Hz to 10-16 Hz and delaying touch commands.

VT100_UI_ENABLED (config.h, off by default) restores the old
behaviour for debugging without a Box-3; status messages become
plain event log lines when disabled.

src/config.h

@@ -110,6 +110,16 @@
 #define LINK_UART_TX_PIN 22
 #define LINK_UART_RX_PIN 21
 
+/*
+ * VT100 serial console UI (TeraTerm/minicom). Superseded by the Box-3
+ * display: each full refresh blocks the core 0 task ~40-50 ms at
+ * 115200 baud, degrading the link STATE rate from 20 Hz down to
+ * 10-16 Hz and delaying touch command handling. Enable only for
+ * debugging without a Box-3 attached; status messages are plain log
+ * lines when disabled.
+ */
+//#define VT100_UI_ENABLED
+
 /* our samplerate */
 #define SAMPLE_RATE 44100
 

src/status_module.cpp

@@ -209,6 +209,7 @@ void Status_PrintAll(void)
 
 void Status_Process(void)
 {
+#ifdef VT100_UI_ENABLED
     status_cnt ++;
     if (status_cnt > 1000 * 3)
     {
@@ -223,6 +224,7 @@ void Status_Process(void)
         loopMeterCount = 0;
         Status_PrintAll();
     }
+#endif
 }
 
 /*
@@ -230,9 +232,14 @@ void Status_Process(void)
  */
 void Status_ValueChangedFloat(const char *descr, float value)
 {
+#ifdef VT100_UI_ENABLED
     status_cnt = 0;
     memset(statusMsg, 0, sizeof(statusMsg));
     sprintf(statusMsg, "%s: %0.2f", descr, value);
+#else
+    /* the Box-3 is the main display: keep events as plain log lines */
+    Serial.printf("[status] %s: %0.2f\n", descr, value);
+#endif
 }
 
 /*
@@ -240,9 +247,13 @@ void Status_ValueChangedFloat(const char *descr, float value)
  */
 void Status_ValueChangedInt(const char *descr, int value)
 {
+#ifdef VT100_UI_ENABLED
     status_cnt = 0;
     memset(statusMsg, 0, sizeof(statusMsg));
     sprintf(statusMsg, "%s: %d", descr, value);
+#else
+    Serial.printf("[status] %s: %d\n", descr, value);
+#endif
 }
 
 /*
@@ -250,7 +261,11 @@ void Status_ValueChangedInt(const char *descr, int value)
  */
 void Status_TestMsg(const char *text)
 {
+#ifdef VT100_UI_ENABLED
     status_cnt = 0;
     memset(statusMsg, 0, sizeof(statusMsg));
     sprintf(statusMsg, "%s", text);
+#else
+    Serial.printf("[status] %s\n", text);
+#endif
 }