chore: prepare verified CRX uploads and release 0.15.4

- Add helper scripts for Chrome Web Store verified CRX uploads using a dedicated RSA upload key protected by GPG.
- Document the verified upload packaging flow and ignore local signing secrets.
- Add npm packaging entry point for signed webstore CRX artifacts.
- Chunk large SDK tab close batches to avoid native-host response timeouts.
- Bump project and extension versions to 0.15.4 with matching tests.

tests/test_api.py

@@ -364,6 +364,27 @@ class TestTabs:
       profile=None, remote=None, key=None,
     )
 
+  def test_tabs_close_by_ids_chunks_large_batches(self, b, mock_send):
+    mock_send.side_effect = [{"closed": 50}, {"closed": 50}, {"closed": 20}]
+    assert b.tabs.close(tab_ids=range(120), gentle_mode="normal") == 120
+    assert mock_send.call_args_list == [
+      call(
+        "tabs.close",
+        {"tabId": None, "tabIds": list(range(0, 50)), "inactive": False, "duplicates": False, "gentleMode": "normal"},
+        profile=None, remote=None, key=None,
+      ),
+      call(
+        "tabs.close",
+        {"tabId": None, "tabIds": list(range(50, 100)), "inactive": False, "duplicates": False, "gentleMode": "normal"},
+        profile=None, remote=None, key=None,
+      ),
+      call(
+        "tabs.close",
+        {"tabId": None, "tabIds": list(range(100, 120)), "inactive": False, "duplicates": False, "gentleMode": "normal"},
+        profile=None, remote=None, key=None,
+      ),
+    ]
+
   def test_tabs_move(self, b, mock_send):
     b.tabs.move(10, forward=True)
     mock_send.assert_called_once_with(