[bluetooth_proxy] Warn about BLE connection timeout mismatch on Arduino framework (#10063)

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

esphome/components/bluetooth_proxy/__init__.py

@@ -1,14 +1,20 @@
+import logging
+
 import esphome.codegen as cg
 from esphome.components import esp32_ble, esp32_ble_client, esp32_ble_tracker
 from esphome.components.esp32 import add_idf_sdkconfig_option
 from esphome.components.esp32_ble import BTLoggers
 import esphome.config_validation as cv
 from esphome.const import CONF_ACTIVE, CONF_ID
+from esphome.core import CORE
+from esphome.log import AnsiFore, color
 
 AUTO_LOAD = ["esp32_ble_client", "esp32_ble_tracker"]
 DEPENDENCIES = ["api", "esp32"]
 CODEOWNERS = ["@jesserockz"]
 
+_LOGGER = logging.getLogger(__name__)
+
 CONF_CONNECTION_SLOTS = "connection_slots"
 CONF_CACHE_SERVICES = "cache_services"
 CONF_CONNECTIONS = "connections"
@@ -41,6 +47,27 @@ def validate_connections(config):
         esp32_ble_tracker.consume_connection_slots(connection_slots, "bluetooth_proxy")(
             config
         )
+
+        # Warn about connection slot waste when using Arduino framework
+        if CORE.using_arduino and connection_slots:
+            _LOGGER.warning(
+                "Bluetooth Proxy with active connections on Arduino framework has suboptimal performance.\n"
+                "If BLE connections fail, they can waste connection slots for 10 seconds because\n"
+                "Arduino doesn't allow configuring the BLE connection timeout (fixed at 30s).\n"
+                "ESP-IDF framework allows setting it to 20s to match client timeouts.\n"
+                "\n"
+                "To switch to ESP-IDF, add this to your YAML:\n"
+                "  esp32:\n"
+                "    framework:\n"
+                "      type: esp-idf\n"
+                "\n"
+                "For detailed migration instructions, see:\n"
+                "%s",
+                color(
+                    AnsiFore.BLUE, "https://esphome.io/guides/esp32_arduino_to_idf.html"
+                ),
+            )
+
         return {
             **config,
             CONF_CONNECTIONS: [CONNECTION_SCHEMA({}) for _ in range(connection_slots)],