Open the OpenBao login in pinned Playwright Chromium.

The Windows default browser presented a signed-in Firefox session. The
launcher now starts coulomb-social's headed Playwright Chromium with a new
empty profile.

Assistant: grok
Assistant-Session: 01a198fa-fd27-7e41-a0a2-57355c3e4efd

tests/test_operator_browser.py

@@ -17,8 +17,26 @@ class BrowserBoundary(unittest.TestCase):
         self.assertFalse(allowed('https://kc.coulomb.social/?redirect_uri=http://localhost:8250/oidc/callback&redirect_uri=https://evil.example'))
     def test_launch_uses_empty_profile(self):
         url='https://kc.coulomb.social/authorize?'+urlencode({'redirect_uri':'http://localhost:8250/oidc/callback'})
-        argv=launch_argv(r'C:\Edge\msedge.exe', r'C:\fresh\profile', url)
-        self.assertEqual(argv[0], r'C:\Edge\msedge.exe')
-        self.assertIn(r'--user-data-dir=C:\fresh\profile', argv)
+        browser='/cache/ms-playwright/chromium-1234/chrome-linux64/chrome'
+        argv=launch_argv(browser, '/tmp/fresh-profile', url)
+        self.assertEqual(argv[0], browser)
+        self.assertIn('--user-data-dir=/tmp/fresh-profile', argv)
         self.assertEqual(argv[-1], url)
-        self.assertNotIn('explorer.exe', ' '.join(argv))
+        self.assertNotIn('--headless', argv)
+        joined=' '.join(argv)
+        for banned in ('explorer.exe', 'powershell', 'msedge', 'firefox', '/mnt/c/'):
+            self.assertNotIn(banned, joined)
+    def test_chromium_comes_from_the_playwright_pin(self):
+        import json
+        import tempfile
+        from pathlib import Path
+        with tempfile.TemporaryDirectory() as raw:
+            root=Path(raw)
+            spec=root/'browsers.json'
+            spec.write_text(json.dumps({'browsers':[{'name':'chromium','revision':'1234'},{'name':'firefox','revision':'1538'}]}))
+            binary=root/'chromium-1234'/'chrome-linux64'/'chrome'
+            binary.parent.mkdir(parents=True)
+            binary.write_text('')
+            binary.chmod(0o755)
+            self.assertEqual(launcher['chromium_executable'](spec, root), str(binary))
+            self.assertEqual(launcher['chromium_executable'](root/'missing.json', root), '')