[packet_transport] Use FixedVector for sensor lists to eliminate realloc machinery

The sensor and binary sensor counts are known at config time, so
pre-allocate with FixedVector::init() instead of using std::vector
which pulls in _M_realloc_insert template instantiation code.

esphome/components/packet_transport/__init__.py

@@ -177,13 +177,19 @@ async def register_packet_transport(var, config):
             cg.add(var.set_provider_encryption(name, hash_encryption_key(encryption)))
 
     is_provider = False
-    for sens_conf in config.get(CONF_SENSORS, ()):
+    sensors = config.get(CONF_SENSORS, ())
+    binary_sensors = config.get(CONF_BINARY_SENSORS, ())
+    if sensors:
+        cg.add(var.set_sensor_count(len(sensors)))
+    if binary_sensors:
+        cg.add(var.set_binary_sensor_count(len(binary_sensors)))
+    for sens_conf in sensors:
         is_provider = True
         sens_id = sens_conf[CONF_ID]
         sensor = await cg.get_variable(sens_id)
         bcst_id = sens_conf.get(CONF_BROADCAST_ID, sens_id.id)
         cg.add(var.add_sensor(bcst_id, sensor))
-    for sens_conf in config.get(CONF_BINARY_SENSORS, ()):
+    for sens_conf in binary_sensors:
         is_provider = True
         sens_id = sens_conf[CONF_ID]
         sensor = await cg.get_variable(sens_id)

esphome/components/packet_transport/packet_transport.cpp

@@ -221,7 +221,7 @@ void PacketTransport::setup() {
   }
 #ifdef USE_SENSOR
   for (auto &sensor : this->sensors_) {
-    // [&sensor] is safe: sensor refers to a vector element that is never modified after setup(),
+    // [&sensor] is safe: sensor refers to a FixedVector element that never reallocates,
     // so the reference remains valid for the component's lifetime.
     sensor.sensor->add_on_state_callback([&sensor](float x) {
       sensor.parent->updated_ = true;
@@ -231,7 +231,7 @@ void PacketTransport::setup() {
 #endif
 #ifdef USE_BINARY_SENSOR
   for (auto &sensor : this->binary_sensors_) {
-    // [&sensor] is safe: sensor refers to a vector element that is never modified after setup(),
+    // [&sensor] is safe: sensor refers to a FixedVector element that never reallocates,
     // so the reference remains valid for the component's lifetime.
     sensor.sensor->add_on_state_callback([&sensor](bool value) {
       sensor.parent->updated_ = true;

esphome/components/packet_transport/packet_transport.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "esphome/core/component.h"
+#include "esphome/core/helpers.h"
 #include "esphome/core/preferences.h"
 #ifdef USE_SENSOR
 #include "esphome/components/sensor/sensor.h"
@@ -71,6 +72,7 @@ class PacketTransport : public PollingComponent {
   void dump_config() override;
 
 #ifdef USE_SENSOR
+  void set_sensor_count(size_t count) { this->sensors_.init(count); }
   void add_sensor(const char *id, sensor::Sensor *sensor) {
     Sensor st{sensor, id, true, this};
     this->sensors_.push_back(st);
@@ -81,6 +83,7 @@ class PacketTransport : public PollingComponent {
   }
 #endif
 #ifdef USE_BINARY_SENSOR
+  void set_binary_sensor_count(size_t count) { this->binary_sensors_.init(count); }
   void add_binary_sensor(const char *id, binary_sensor::BinarySensor *sensor) {
     BinarySensor st{sensor, id, true, this};
     this->binary_sensors_.push_back(st);
@@ -152,11 +155,11 @@ class PacketTransport : public PollingComponent {
   std::vector<uint8_t> encryption_key_{};
 
 #ifdef USE_SENSOR
-  std::vector<Sensor> sensors_{};
+  FixedVector<Sensor> sensors_{};
   string_map_t<string_map_t<sensor::Sensor *>> remote_sensors_{};
 #endif
 #ifdef USE_BINARY_SENSOR
-  std::vector<BinarySensor> binary_sensors_{};
+  FixedVector<BinarySensor> binary_sensors_{};
   string_map_t<string_map_t<binary_sensor::BinarySensor *>> remote_binary_sensors_{};
 #endif