[api] Fix CI errors in MAC varint unit tests

- Test file: declare proto_debug_end_ locally instead of misusing
  PROTO_ENCODE_DEBUG_INIT (which expands to a comma+expression for
  appending to a function call, not a standalone statement). Add
  NOLINTNEXTLINE on the deterministic mt19937_64 seed so clang-tidy
  cert-msc32-c stops failing the build (the seed is intentional for
  reproducible test runs).

- socket FILTER_SOURCE_FILES: tolerate non-dict CORE.config['socket']
  (e.g. C++ unit-test builds where socket isn't validated as a
  mapping). Returning [] is safe -- all impl files are guarded by
  USE_SOCKET_IMPL_* defines so only the selected one contributes
  code.

esphome/components/socket/__init__.py

@@ -177,7 +177,14 @@ async def to_code(config):
 
 def FILTER_SOURCE_FILES() -> list[str]:
     """Return list of socket implementation files that aren't selected by the user."""
-    impl = CORE.config["socket"][CONF_IMPLEMENTATION]
+    socket_config = CORE.config.get("socket")
+    if not isinstance(socket_config, dict):
+        # Config has not been validated yet (or socket isn't configured as a
+        # mapping for this build, e.g. a C++ unit test build that skips config
+        # validation). Don't filter -- all impl files are guarded by USE_*
+        # defines so only the selected implementation contributes code anyway.
+        return []
+    impl = socket_config[CONF_IMPLEMENTATION]
 
     # Build list of files to exclude based on selected implementation
     excluded = []

tests/components/api/test_proto_mac_varint.cpp

@@ -1,6 +1,7 @@
 #include <gtest/gtest.h>
 
 #include <cstdint>
+#include <ios>
 #include <random>
 
 #include "esphome/components/api/api_buffer.h"
@@ -55,7 +56,9 @@ static void verify_mac(uint64_t mac, size_t expected_bytes) {
   APIBuffer api_buf;
   api_buf.resize(16);
   uint8_t *pos = api_buf.data();
-  PROTO_ENCODE_DEBUG_INIT(&api_buf);
+#ifdef ESPHOME_DEBUG_API
+  uint8_t *proto_debug_end_ = api_buf.data() + api_buf.size();
+#endif
   ProtoEncode::encode_varint_raw_48bit(pos PROTO_ENCODE_DEBUG_ARG, mac);
   size_t new_len = pos - api_buf.data();
 
@@ -109,6 +112,7 @@ TEST(ProtoMacVarint, AllOnes) { verify_mac(0xFFFFFFFFFFFFULL, 7); }         // F
 
 // 100 deterministic-random 48-bit MACs to catch regressions across the space.
 TEST(ProtoMacVarint, RandomSample) {
+  // NOLINTNEXTLINE(cert-msc32-c,cert-msc51-cpp) -- intentional fixed seed for reproducibility.
   std::mt19937_64 rng(0xC0FFEE);
   for (int i = 0; i < 100; i++) {
     uint64_t mac = rng() & 0xFFFFFFFFFFFFULL;