fix(install): skip browser download when system chromium exists

tests/tools/test_browser_chromium_check.py

@@ -41,6 +41,16 @@ class TestChromiumSearchRoots:
 
 
 class TestChromiumInstalled:
+    def test_true_when_plain_chromium_on_path(self, monkeypatch):
+        monkeypatch.delenv("AGENT_BROWSER_EXECUTABLE_PATH", raising=False)
+        monkeypatch.setattr(
+            bt.shutil,
+            "which",
+            lambda name: "/usr/bin/chromium" if name == "chromium" else None,
+        )
+
+        assert bt._chromium_installed() is True
+
     def test_true_when_chromium_dir_present(self, monkeypatch, tmp_path):
         monkeypatch.setenv("PLAYWRIGHT_BROWSERS_PATH", str(tmp_path))
         (tmp_path / "chromium-1208").mkdir()
@@ -108,4 +118,3 @@ class TestRunBrowserCommandChromiumGuard:
     """
 
 
-