Include noise.h under the spare ephemeral define and assert the empty slot precondition

esphome/components/api/api_server.h

@@ -5,7 +5,7 @@
 #include "api_buffer.h"
 // Must precede clients_ so APIConnection is complete for default_delete (libc++).
 #include "api_connection.h"
-#ifdef USE_API_NOISE
+#if defined(USE_API_NOISE) || defined(USE_NOISE_SPARE_EPHEMERAL)
 // Only present in the build when the noise component is loaded
 #include "esphome/components/noise/noise.h"
 #endif

tests/components/noise/test_noise_handshake.cpp

@@ -177,6 +177,7 @@ static void run_handshake(NoiseResponderHandshake &responder, uint8_t responder_
 }
 
 TEST(SpareEphemeralTest, EmptySlotLeavesHandshakeToGenerate) {
+  ASSERT_FALSE(has_spare_ephemeral());
   NoiseResponderHandshake responder;
   uint8_t responder_e[32];
   run_handshake(responder, responder_e);