fix clang-tidy warnings

- Add NOLINT for intentional global mutable state
- Simplify boolean return in parse_posix_tz
- Add USE_TIME_TIMEZONE define for tests
- Add NOLINT for Google Test SetUp/TearDown methods

esphome/components/time/posix_tz.cpp

@@ -8,6 +8,7 @@
 namespace esphome::time {
 
 // Global timezone - set once at startup, rarely changes
+// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables) - intentional mutable state
 static ParsedTimezone global_tz_{};
 
 void set_global_tz(const ParsedTimezone &tz) { global_tz_ = tz; }
@@ -430,12 +431,8 @@ bool parse_posix_tz(const char *tz_string, ParsedTimezone &result) {
     return false;
   }
   p++;
-  if (!internal::parse_dst_rule(p, result.dst_end)) {
-    return false;
-  }
-
   // has_dst() now returns true since dst_start.type was set by parse_dst_rule
-  return true;
+  return internal::parse_dst_rule(p, result.dst_end);
 }
 
 bool epoch_to_local_tm(time_t utc_epoch, const ParsedTimezone &tz, struct tm *out_tm) {

tests/components/time/posix_tz_parser.cpp

@@ -1,6 +1,9 @@
 // Tests for the POSIX TZ parser and ESPTime::strptime implementations
 // These custom parsers avoid pulling in scanf (~9.8KB on ESP32-IDF).
 
+// Enable USE_TIME_TIMEZONE for tests
+#define USE_TIME_TIMEZONE
+
 #include <gtest/gtest.h>
 #include <cstdlib>
 #include <ctime>
@@ -752,6 +755,7 @@ TEST(PosixTzParser, EpochToLocalDstTransition) {
 
 class LibcVerificationTest : public ::testing::TestWithParam<std::tuple<const char *, time_t>> {
  protected:
+  // NOLINTNEXTLINE(readability-identifier-naming) - Google Test requires this name
   void SetUp() override {
     // Save current TZ
     const char *current_tz = getenv("TZ");
@@ -759,6 +763,7 @@ class LibcVerificationTest : public ::testing::TestWithParam<std::tuple<const ch
     had_tz_ = current_tz != nullptr;
   }
 
+  // NOLINTNEXTLINE(readability-identifier-naming) - Google Test requires this name
   void TearDown() override {
     // Restore TZ
     if (had_tz_) {