fix: separate screen-only logging from file logging

- Add log_write_screen() for status/stats output (stderr only)
- Change STATUS line to use log_write_screen (not in log file)
- SIGNAL, ORDER, FILL, FILLED/FAILED still go to both screen and log file
- Log file at /tmp/engine.log

src/evaluate.c

@@ -170,7 +170,7 @@ bool evaluate_symbol(evaluator_t *ev, uint16_t symbol_idx, int64_t t_sock_arrive
         int64_t now = now_ms();
         if (now - last_status_ms >= 30000) {
             last_status_ms = now;
-            log_write("[STATUS] evals=%lu signals=%lu "
+            log_write_screen("[STATUS] evals=%lu signals=%lu "
                     "best=%.2f bps (%s) | %u triangles\n",
                     (unsigned long)ev->stats.triangles_evaluated,
                     (unsigned long)ev->stats.signals_fired,

src/log.c

@@ -106,3 +106,11 @@ void log_write(const char *fmt, ...) {
         write(log_pipe[1], buf, (size_t)total);
     }
 }
+
+/* Write to stderr only — skip the log file. */
+void log_write_screen(const char *fmt, ...) {
+    va_list ap;
+    va_start(ap, fmt);
+    vfprintf(stderr, fmt, ap);
+    va_end(ap);
+}

src/log.h

@@ -9,10 +9,14 @@ void log_init(void);
 /* Shut down the writer thread and close the pipe. */
 void log_shutdown(void);
 
-/* Write a formatted log line to stderr with timestamp and newline.
+/* Write a formatted log line to stderr AND log file (if configured).
  * Non-blocking after log_init(); falls back to synchronous fprintf. */
 void log_write(const char *fmt, ...) __attribute__((format(printf, 1, 2)));
 
+/* Write to stderr ONLY (skip log file). For status/stats that shouldn't
+ * clutter the execution log file. */
+void log_write_screen(const char *fmt, ...) __attribute__((format(printf, 1, 2)));
+
 /* Set a log file path. Must be called before the first log_write. */
 void log_set_file(const char *path);