perf(bot): lower body once and strstr instead of O(n*m) per-offset tolower

For a 140-byte channel msg with a 64-byte trigger, the old loop did
~8960 tolower() calls per inbound message; now it's 140 tolower calls
plus one strstr.

perf(buzzer): skip nRF52 STOPPED wait when PWM was not running

TASKS_STOP on a disabled PWM never fires EVENTS_STOPPED, so the wait
always timed out at 2 ms. Gating on _pwm_on removes the wait on the
first note of a melody and after pauses, where there's nothing to wait
for.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

examples/companion_radio/MyMeshBot.h

@@ -8,15 +8,13 @@ void MyMesh::tryBotReplyDM(const ContactInfo& from, const char* text) {
         millis() - _bot_last_dm_reply_ms > 10000UL))
     return;
 
-  const char* tr = _prefs.bot_trigger;  // already lowercase (normalised at save/load time)
+  // Lower-case the body once, then a single strstr — avoids O(n*m) tolower per offset.
-  int tlen = strlen(tr);
+  char low[200];
-  bool matched = false;
+  size_t n = strlen(text);
-  for (const char* t = text; *t && !matched; t++) {
+  if (n >= sizeof(low)) n = sizeof(low) - 1;
-    int i = 0;
+  for (size_t i = 0; i < n; i++) low[i] = (char)tolower((uint8_t)text[i]);
-    while (i < tlen && tolower((uint8_t)t[i]) == (uint8_t)tr[i]) i++;
+  low[n] = '\0';
-    if (i == tlen) matched = true;
+  if (!strstr(low, _prefs.bot_trigger)) return;
-  }
-  if (!matched) return;
 
   uint32_t ts = getRTCClock()->getCurrentTime();
   char expanded[200];
@@ -45,15 +43,12 @@ void MyMesh::tryBotReplyChannel(uint8_t channel_idx, const char* text) {
   const char* sep = strstr(text, ": ");
   if (sep) msg = sep + 2;
 
-  const char* tr = _prefs.bot_trigger;  // already lowercase (normalised at save/load time)
+  char low[200];
-  int tlen = strlen(tr);
+  size_t n = strlen(msg);
-  bool matched = false;
+  if (n >= sizeof(low)) n = sizeof(low) - 1;
-  for (const char* t = msg; *t && !matched; t++) {
+  for (size_t i = 0; i < n; i++) low[i] = (char)tolower((uint8_t)msg[i]);
-    int i = 0;
+  low[n] = '\0';
-    while (i < tlen && tolower((uint8_t)t[i]) == (uint8_t)tr[i]) i++;
+  if (!strstr(low, _prefs.bot_trigger)) return;
-    if (i == tlen) matched = true;
-  }
-  if (!matched) return;
 
   ChannelDetails ch;
   if (!getChannel(channel_idx, ch)) return;

src/helpers/ui/buzzer.cpp

@@ -104,11 +104,14 @@ void genericBuzzer::_nrfStartPwm(uint16_t freq) {
     _duty_buf = 0x8000U | cmp;
     __DMB();
 
+    // Only wait for STOPPED if PWM was actually running — TASKS_STOP on a disabled
+    // PWM never fires EVENTS_STOPPED, so the wait would always time out at 2 ms.
+    if (_pwm_on) {
       NRF_PWM2->TASKS_STOP = 1;
-    // Wait for STOPPED (short busy-wait, typically < 1 PWM period)
       uint32_t t = millis();
       while (!(NRF_PWM2->EVENTS_STOPPED) && (millis() - t) < 2) {}
       NRF_PWM2->EVENTS_STOPPED = 0;
+    }
 
     NRF_PWM2->PSEL.OUT[0] = nrf_pin;
     NRF_PWM2->PSEL.OUT[1] = 0xFFFFFFFFUL;