[mdns] Address review feedback: tighten guards, comments, validator

- Drop redundant wifi_component.h / ethernet_component.h includes from the platform
  .cpp files — mdns_component.h already pulls them in transitively under their
  listener defines.
- Guard initialized_ with USE_RP2040 && USE_MDNS_EVENT_DRIVEN_POLLING instead of
  USE_RP2040 alone, making the coupling with the listener-driven path explicit.
- Short comment on mdns_pump_update noting ODR is preserved by
  FILTER_SOURCE_FILES compiling exactly one platform cpp per build.
- Inline comment on ESP8266 setup() noting AFTER_CONNECTION priority is why the
  unconditional start_polling_window_() is safe.
- Collapse the disabled/platform early-return in _require_network_interface; drop
  the redundant CORE.using_arduino check (ESP8266/RP2040 are always Arduino).
- Add USE_MDNS_EVENT_DRIVEN_POLLING and USE_MDNS_WIFI_LISTENER to defines.h for
  static-analysis discoverability (ethernet listener is mutually exclusive with
  wifi on these platforms, so one representative is enough).

esphome/components/mdns/__init__.py

@@ -70,9 +70,7 @@ def _require_network_interface(config: ConfigType) -> ConfigType:
     window. Reject at config time rather than silently producing a component
     that never initializes.
     """
-    if config.get(CONF_DISABLED):
-        return config
-    if not CORE.using_arduino or not (CORE.is_esp8266 or CORE.is_rp2040):
+    if config.get(CONF_DISABLED) or not (CORE.is_esp8266 or CORE.is_rp2040):
         return config
     full_config = fv.full_config.get()
     has_wifi = "wifi" in full_config

esphome/components/mdns/mdns_component.h

@@ -25,8 +25,8 @@
 namespace esphome::mdns {
 
 #ifdef USE_MDNS_EVENT_DRIVEN_POLLING
-/// Platform-specific MDNS.update() trampoline. Defined in mdns_<platform>.cpp so the
-/// shared code can schedule it without including the platform's mDNS header.
+/// MDNS.update() trampoline. Defined in exactly one mdns_<platform>.cpp per build
+/// (FILTER_SOURCE_FILES in __init__.py enforces this), so ODR is preserved.
 void mdns_pump_update();
 #endif
 
@@ -159,7 +159,8 @@ class MDNSComponent final : public Component
 #ifdef USE_MDNS_STORE_SERVICES
   StaticVector<MDNSService, MDNS_SERVICE_COUNT> services_{};
 #endif
-#ifdef USE_RP2040
+#if defined(USE_RP2040) && defined(USE_MDNS_EVENT_DRIVEN_POLLING)
+  // RP2040 defers MDNS.begin() until the first IP-up event; this tracks that.
   bool initialized_{false};
 #endif
   void compile_records_(StaticVector<MDNSService, MDNS_SERVICE_COUNT> &services, char *mac_address_buf);

esphome/components/mdns/mdns_esp8266.cpp

@@ -8,9 +8,8 @@
 #include "esphome/core/hal.h"
 #include "esphome/core/log.h"
 #include "mdns_component.h"
-#ifdef USE_MDNS_EVENT_DRIVEN_POLLING
-#include "esphome/components/wifi/wifi_component.h"
-#endif
+// wifi_component.h is pulled in transitively by mdns_component.h when
+// USE_MDNS_WIFI_LISTENER is defined.
 
 namespace esphome::mdns {
 
@@ -46,8 +45,9 @@ void mdns_pump_update() { MDNS.update(); }
 void MDNSComponent::setup() {
   this->setup_buffers_and_register_(register_esp8266);
 #ifdef USE_MDNS_EVENT_DRIVEN_POLLING
-  // LEAmDNS's own LwipIntf::statusChangeCB drives _restart() on netif changes; we only
-  // need to arm the polling window around the initial probe/announce and each reconnect.
+  // LEAmDNS's own LwipIntf::statusChangeCB drives _restart() on netif changes; we just
+  // arm the window around the initial probe/announce and each reconnect. Unconditional
+  // here is safe: setup_priority::AFTER_CONNECTION guarantees the network is up.
   wifi::global_wifi_component->add_ip_state_listener(this);
   this->start_polling_window_();
 #endif

esphome/components/mdns/mdns_rp2040.cpp

@@ -6,12 +6,8 @@
 #include "esphome/core/application.h"
 #include "esphome/core/log.h"
 #include "mdns_component.h"
-#ifdef USE_MDNS_WIFI_LISTENER
-#include "esphome/components/wifi/wifi_component.h"
-#endif
-#ifdef USE_MDNS_ETHERNET_LISTENER
-#include "esphome/components/ethernet/ethernet_component.h"
-#endif
+// wifi_component.h / ethernet_component.h are pulled in transitively by
+// mdns_component.h when their respective listener defines are active.
 
 // Arduino-Pico's PolledTimeout.h (pulled in by ESP8266mDNS.h) redefines IRAM_ATTR to empty.
 #pragma push_macro("IRAM_ATTR")

esphome/core/defines.h

@@ -111,6 +111,8 @@
 #define MDNS_SERVICE_COUNT 3
 #define USE_MDNS_DYNAMIC_TXT
 #define MDNS_DYNAMIC_TXT_COUNT 2
+#define USE_MDNS_EVENT_DRIVEN_POLLING
+#define USE_MDNS_WIFI_LISTENER
 #define MICRONOVA_LISTENER_COUNT 1
 #define USE_MICRONOVA_WRITER
 #define SERIAL_PROXY_COUNT 2