fix(native): implement BinarySemaphorePosix with proper pthread synchronization (#9895)

* fix(native): implement BinarySemaphorePosix with proper pthread synchronization

The BinarySemaphorePosix class (used on all Linux/portduino/native builds)
had stub implementations: give() was a no-op and take() just called
delay(msec) and returned false. This broke the cooperative thread scheduler
on native platforms — threads could not wake the main loop, radio RX
interrupts were missed, and telemetry never transmitted over the mesh.

Replace the stubs with a proper binary semaphore using pthread_mutex_t +
pthread_cond_t + bool signaled:

- take(msec): pthread_cond_timedwait with CLOCK_REALTIME timeout, consumes
  signal atomically (binary semaphore semantics)
- give(): sets signaled=true, signals condition variable
- giveFromISR(): delegates to give(), sets pxHigherPriorityTaskWoken

Tested on Raspberry Pi 3 Model B (ARM64, Debian Bookworm) with Adafruit
LoRa Radio Bonnet (SX1276). Before fix: no radio TX/RX, no telemetry on
mesh. After fix: bidirectional LoRa, MQTT gateway, telemetry all working.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* ARCH_PORTDUINO

* Refactor BinarySemaphorePosix header for ARCH_PORTDUINO

* Change preprocessor directive from ifndef to ifdef

* Gate new Semaphore code to Portduino and fix STM compilation

* Binary Semaphore Posix better error handling

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Ben Meadors <benmmeadors@gmail.com>
Co-authored-by: Jonathan Bennett <jbennett@incomsystems.biz>

src/concurrency/BinarySemaphorePosix.cpp

@@ -1,10 +1,85 @@
 #include "concurrency/BinarySemaphorePosix.h"
 #include "configuration.h"
 
+#include <errno.h>
+#include <sys/time.h>
+
 #ifndef HAS_FREE_RTOS
 
 namespace concurrency
 {
+#ifdef ARCH_PORTDUINO
+
+BinarySemaphorePosix::BinarySemaphorePosix()
+{
+    if (pthread_mutex_init(&mutex, NULL) != 0) {
+        throw std::runtime_error("pthread_mutex_init failed");
+    }
+    if (pthread_cond_init(&cond, NULL) != 0) {
+        pthread_mutex_destroy(&mutex);
+        throw std::runtime_error("pthread_cond_init failed");
+    }
+    signaled = false;
+}
+
+BinarySemaphorePosix::~BinarySemaphorePosix()
+{
+    pthread_cond_destroy(&cond);
+    pthread_mutex_destroy(&mutex);
+}
+
+/**
+ * Returns false if we timed out
+ */
+bool BinarySemaphorePosix::take(uint32_t msec)
+{
+    pthread_mutex_lock(&mutex);
+
+    if (!signaled) {
+        struct timespec ts;
+        clock_gettime(CLOCK_REALTIME, &ts);
+
+        ts.tv_sec += msec / 1000;
+        ts.tv_nsec += (msec % 1000) * 1000000L;
+        if (ts.tv_nsec >= 1000000000L) {
+            ts.tv_sec += 1;
+            ts.tv_nsec -= 1000000000L;
+        }
+
+        while (!signaled) {
+            int rc = pthread_cond_timedwait(&cond, &mutex, &ts);
+            if (rc == ETIMEDOUT)
+                break;
+            if (rc != 0) {
+                // Some other error occurred
+                pthread_mutex_unlock(&mutex);
+                throw std::runtime_error("pthread_cond_timedwait failed: " + std::to_string(rc));
+            }
+        }
+    }
+
+    bool wasSignaled = signaled;
+    signaled = false; // consume the signal (binary semaphore)
+
+    pthread_mutex_unlock(&mutex);
+    return wasSignaled;
+}
+
+void BinarySemaphorePosix::give()
+{
+    pthread_mutex_lock(&mutex);
+    signaled = true;
+    pthread_cond_signal(&cond);
+    pthread_mutex_unlock(&mutex);
+}
+
+IRAM_ATTR void BinarySemaphorePosix::giveFromISR(BaseType_t *pxHigherPriorityTaskWoken)
+{
+    give();
+    if (pxHigherPriorityTaskWoken)
+        *pxHigherPriorityTaskWoken = true;
+}
+#else
 
 BinarySemaphorePosix::BinarySemaphorePosix() {}
 
@@ -22,7 +97,8 @@ bool BinarySemaphorePosix::take(uint32_t msec)
 void BinarySemaphorePosix::give() {}
 
 IRAM_ATTR void BinarySemaphorePosix::giveFromISR(BaseType_t *pxHigherPriorityTaskWoken) {}
+#endif
 
 } // namespace concurrency
 
-#endif
+#endif

src/concurrency/BinarySemaphorePosix.h

@@ -2,6 +2,10 @@
 
 #include "../freertosinc.h"
 
+#ifdef ARCH_PORTDUINO
+#include <pthread.h>
+#endif
+
 namespace concurrency
 {
 
@@ -9,7 +13,12 @@ namespace concurrency
 
 class BinarySemaphorePosix
 {
-    // SemaphoreHandle_t semaphore;
+
+#ifdef ARCH_PORTDUINO
+    pthread_mutex_t mutex;
+    pthread_cond_t cond;
+    bool signaled;
+#endif
 
   public:
     BinarySemaphorePosix();
@@ -27,4 +36,4 @@ class BinarySemaphorePosix
 
 #endif
 
-} // namespace concurrency
+} // namespace concurrency