fix: LS-1 close queued handlers on re-setup; LS-2 register atexit once

LS-1: re-setup closes the QueueListener's wrapped file/console handlers after stopping it
(was: relied on GC). LS-2: atexit registration guarded by a module flag so repeated
queue=True re-setups don't stack callbacks. JSON formatter caches the rendered traceback on
the record (no per-handler re-render); _move dest precondition documented.

Signed-off-by: disqualifier <dev@disqualifier.me>

src/log_setup/formats.py

@@ -46,7 +46,11 @@ class JsonLinesFormatter(logging.Formatter):
             if key not in _RESERVED and key not in _OUTPUT_KEYS and not key.startswith("_"):
                 payload[key] = value
         if record.exc_info:
-            payload["exc_info"] = self.formatException(record.exc_info)
+            # cache the rendered traceback on the record (as stdlib Formatter does) so a
+            # second handler/format() of the same record doesn't re-render it
+            if not record.exc_text:
+                record.exc_text = self.formatException(record.exc_info)
+            payload["exc_info"] = record.exc_text
         elif record.exc_text:
             payload["exc_info"] = record.exc_text
         if record.stack_info:

src/log_setup/rotation.py

@@ -20,6 +20,11 @@ def _move(source: str, dest: str) -> None:
     different filesystems — exactly the container bind-mount / separate-logs-volume
     case this lib targets. fall back to shutil.move (copy+unlink) so the roll still
     lands instead of failing every rotation via the handler's silent handleError.
+
+    precondition: `dest` is a free, non-directory path (all call sites generate a unique
+    timestamped/dated dest). os.replace and shutil.move differ on a dest that already
+    exists as a directory, so this helper is not safe for arbitrary dests — only the
+    rotation paths that guarantee a fresh file dest.
     """
     try:
         os.replace(source, dest)

src/log_setup/setup.py

@@ -22,6 +22,7 @@ log = logging.getLogger(__name__)
 
 _MARKER = "_log_setup_owned"
 _listener = None
+_atexit_registered = False
 
 
 def _level_value(level: Union[int, str]) -> int:
@@ -80,6 +81,14 @@ def _clear_owned(root: logging.Logger) -> None:
     global _listener
     if _listener is not None:
         _listener.stop()
+        # the listener owns the real file/console handlers (only the QueueHandler is
+        # root-attached + marked); stopping it doesn't close them, so close them here
+        # to avoid relying on GC finalizers across a re-setup
+        for wrapped in getattr(_listener, "handlers", ()):
+            try:
+                wrapped.close()
+            except Exception:
+                log.warning("log_setup: failed to close queued handler %r", wrapped, exc_info=True)
         _listener = None
     for handler in list(root.handlers):
         if getattr(handler, _MARKER, False):
@@ -160,7 +169,7 @@ def setup_logging(
     unwritable `log_dir` falls back to console-only with a warning even when `console` is
     off, so output is never silently lost; an unknown `output` falls back to text.
     """
-    global _listener
+    global _listener, _atexit_registered
 
     root = logging.getLogger()
     root.setLevel(_level_value(level))
@@ -197,7 +206,11 @@ def setup_logging(
         root.addHandler(qh)
         _listener = logging.handlers.QueueListener(record_queue, *handlers, respect_handler_level=True)
         _listener.start()
-        atexit.register(_stop_listener)
+        if not _atexit_registered:
+            # register once — atexit doesn't dedupe, so repeated queue re-setups would
+            # otherwise stack identical callbacks (harmless but unbounded)
+            atexit.register(_stop_listener)
+            _atexit_registered = True
     else:
         for handler in handlers:
             root.addHandler(_tag(handler))