[core] Remove cv.only_with_esp_idf and CORE.using_esp_idf (#16681)

esphome/config_validation.py

@@ -857,16 +857,6 @@ only_on_rp2040 = only_on(PLATFORM_RP2040)
 only_with_arduino = only_with_framework(Framework.ARDUINO)
 
 
-def only_with_esp_idf(obj):
-    """Deprecated: use only_on_esp32 instead."""
-    _LOGGER.warning(
-        "cv.only_with_esp_idf was deprecated in 2026.1, will change behavior in 2026.6. "
-        "ESP32 Arduino builds on top of ESP-IDF, so ESP-IDF features are available in both frameworks. "
-        "Use cv.only_on_esp32 and/or cv.only_with_arduino instead."
-    )
-    return only_with_framework(Framework.ESP_IDF)(obj)
-
-
 # Adapted from:
 # https://github.com/alecthomas/voluptuous/issues/115#issuecomment-144464666
 def has_at_least_one_key(*keys):

esphome/core/__init__.py

@@ -859,15 +859,6 @@ class EsphomeCore:
     def using_arduino(self):
         return self.target_framework == "arduino"
 
-    @property
-    def using_esp_idf(self):
-        _LOGGER.warning(
-            "CORE.using_esp_idf was deprecated in 2026.1, will change behavior in 2026.6. "
-            "ESP32 Arduino builds on top of ESP-IDF, so ESP-IDF features are available in both frameworks. "
-            "Use CORE.is_esp32 and/or CORE.using_arduino instead."
-        )
-        return self.target_framework == "esp-idf"
-
     @property
     def using_toolchain_esp_idf(self):
         return self.toolchain == Toolchain.ESP_IDF