[ld2450] Batch UART reads to reduce loop overhead

Read all available bytes in batches via read_array() instead of
byte-at-a-time read() calls. Each read() internally chains through
read_byte -> read_array(1) -> check_read_timeout_ -> available(),
resulting in 3 UART calls per byte. At 256000 baud with ~235 bytes
per loop iteration, this was ~706 UART operations per loop call.
Batching reduces this to ~12.

Measured 33% reduction in loop time (2348ms -> 1577ms per 60s).

esphome/components/ld2450/ld2450.cpp

@@ -276,8 +276,23 @@ void LD2450Component::dump_config() {
 }
 
 void LD2450Component::loop() {
-  while (this->available()) {
-    this->readline_(this->read());
+  int avail = this->available();
+  if (avail == 0) {
+    return;
+  }
+
+  // Read all available bytes in batches to reduce UART call overhead.
+  uint8_t buf[MAX_LINE_LENGTH];
+  while (avail > 0) {
+    size_t to_read = std::min(static_cast<size_t>(avail), sizeof(buf));
+    if (!this->read_array(buf, to_read)) {
+      break;
+    }
+    avail -= to_read;
+
+    for (size_t i = 0; i < to_read; i++) {
+      this->readline_(buf[i]);
+    }
   }
 }
 

esphome/components/modbus/modbus.cpp

@@ -19,27 +19,16 @@ void Modbus::setup() {
 void Modbus::loop() {
   const uint32_t now = App.get_loop_component_start_time();
 
-  int avail = this->available();
-  if (avail > 0) {
-    // Read all available bytes in batches to reduce UART call overhead.
-    uint8_t buf[64];
-    while (avail > 0) {
-      size_t to_read = std::min(static_cast<size_t>(avail), sizeof(buf));
-      if (!this->read_array(buf, to_read)) {
-        break;
-      }
-      avail -= to_read;
-
-      for (size_t i = 0; i < to_read; i++) {
-        if (this->parse_modbus_byte_(buf[i])) {
-          this->last_modbus_byte_ = now;
-        } else {
-          size_t at = this->rx_buffer_.size();
-          if (at > 0) {
-            ESP_LOGV(TAG, "Clearing buffer of %d bytes - parse failed", at);
-            this->rx_buffer_.clear();
-          }
-        }
+  while (this->available()) {
+    uint8_t byte;
+    this->read_byte(&byte);
+    if (this->parse_modbus_byte_(byte)) {
+      this->last_modbus_byte_ = now;
+    } else {
+      size_t at = this->rx_buffer_.size();
+      if (at > 0) {
+        ESP_LOGV(TAG, "Clearing buffer of %d bytes - parse failed", at);
+        this->rx_buffer_.clear();
       }
     }
   }