fix(docker): discover Playwright headless_shell browser (#35717)

Co-authored-by: Nic <nicsequenzy@gmail.com>

tests/test_docker_stage2_browser_discovery.py

@@ -0,0 +1,19 @@
+"""Regression tests for Docker stage2 browser executable discovery."""
+
+from pathlib import Path
+
+
+def test_stage2_discovers_playwright_arm64_headless_shell() -> None:
+    """Playwright's --only-shell layout may use a headless_shell basename."""
+    script = Path("docker/stage2-hook.sh").read_text()
+
+    assert "-name 'headless_shell'" in script
+
+
+def test_stage2_discovery_stays_filename_matched() -> None:
+    """Avoid broad path grep that can pick executable shared libraries."""
+    script = Path("docker/stage2-hook.sh").read_text()
+
+    discovery_block = script.split("browser_bin=$(", 1)[1].split(")\n    if", 1)[0]
+    assert "find \"$PLAYWRIGHT_BROWSERS_PATH\" -type f -executable" in discovery_block
+    assert "grep" not in discovery_block