test(firmware): event_log boot recovery — partial fill and post-wrap

Exercises the slot-scan logic in event_log_init(): after a simulated
reboot (RAM state cleared, NVS slots preserved) the module must
resume with the correct head/cnt so newest-first read order is
unchanged and subsequent writes continue the seq monotonically.

Adds native-only event_log_test_simulate_reboot() helper. Lifts the
slot-scan loop out of the #ifdef ARDUINO guard so the native stub
exercises the same recovery path as production; the platform-specific
NVS setup remains guarded.

firmware/lib/event_log/event_log.cpp

@@ -27,6 +27,11 @@
       g_head = 0;
       g_cnt  = 0;
   }
+  extern "C" void event_log_test_simulate_reboot() {
+      // Simulate device reboot: clear in-RAM state, keep persistent slots.
+      g_head = 0;
+      g_cnt  = 0;
+  }
 #endif
 
 static const size_t SLOTS     = 32;
@@ -69,6 +74,7 @@ void event_log_init() {
         Serial.println("[evlog] NVS begin failed");
         return;
     }
+#endif
     // Scan all 32 slots; locate the one with the largest seq.
     // Empty log: every slot tag == 0 (not a valid EventLogTag, which starts at 1).
     uint32_t max_seq = 0;
@@ -91,9 +97,6 @@ void event_log_init() {
         g_head = 0;
         g_cnt  = 0;
     }
-#else
-    // nothing
-#endif
 }
 
 void event_log_write(EventLogTag tag, uint16_t data0, uint16_t data1) {

firmware/lib/event_log/event_log.h

@@ -33,6 +33,7 @@ struct EventLogEntry {
 static_assert(sizeof(EventLogEntry) == 32, "EventLogEntry must be 32 bytes");
 
 // NVS-backed 32-slot ring buffer. Safe to call before NTP sync.
+// Call exactly once from application setup, before any task writes events.
 void event_log_init();
 void event_log_write(EventLogTag tag, uint16_t data0 = 0, uint16_t data1 = 0);
 size_t event_log_read_recent(EventLogEntry* out, size_t max_entries);