Address PR review comments: rename to __main__.py, improve config examples, document save freeze

src/clip_annotator/annotator.py

@@ -159,7 +159,7 @@ class Annotator(QMainWindow):
 
         self.btn_prev = QPushButton("Previous")
         self.btn_prev.setEnabled(False)
-        btn_next = QPushButton("Next")
+        self.btn_next = QPushButton("Next")
         btn_skip = QPushButton("Skip")
         btn_clear = QPushButton("Clear")
         btn_undo = QPushButton("Undo")
@@ -172,7 +172,7 @@ class Annotator(QMainWindow):
         row1 = QHBoxLayout()
         for b in [
             self.btn_prev,
-            btn_next,
+            self.btn_next,
             btn_skip,
             btn_load_prev_mask,
             btn_auto_segment,
@@ -251,7 +251,7 @@ class Annotator(QMainWindow):
         self.setCentralWidget(container)
 
         self.btn_prev.clicked.connect(self.prev_clip)
-        btn_next.clicked.connect(self.next_clip)
+        self.btn_next.clicked.connect(self.next_clip)
         btn_skip.clicked.connect(self.skip_clip)
         btn_clear.clicked.connect(self.mc.clear)
         btn_undo.clicked.connect(self.mc.undo)
@@ -350,6 +350,16 @@ class Annotator(QMainWindow):
             self.fs.pipe(out_path, buf.getvalue())
 
     # ── actions ────────────────────────────────────────────────────
+    def _save_locked(self):
+        self.btn_next.setEnabled(False)
+        self.btn_prev.setEnabled(False)
+        QApplication.processEvents()
+        try:
+            self.save()
+        finally:
+            self.btn_next.setEnabled(True)
+            self.btn_prev.setEnabled(self.history_pos > 0)
+
     def save(self):
         out = fsjoin(self.out_dir, fsstem(self.filename))
         self._fs_makedirs(out)
@@ -421,7 +431,7 @@ class Annotator(QMainWindow):
     def prev_clip(self):
         if self.history_pos <= 0:
             return
-        self.save()
+        self._save_locked()
         self.history_pos -= 1
         self._load_clip(path=self.history[self.history_pos])
         self._switch_ui_to_clip()
@@ -446,13 +456,13 @@ class Annotator(QMainWindow):
             msg.exec()
             clicked = msg.clickedButton()
             if clicked == btn_replace:
-                self.save()
+                self._save_locked()
                 self._advance_clip()
             elif clicked == btn_keep:
                 self._advance_clip()
             # Cancel: do nothing
         else:
-            self.save()
+            self._save_locked()
             self._advance_clip()
 
     def skip_clip(self):