feat: harden remote serve and reuse connections

- Gate TCP serve commands with safe-by-default policies, per-key allow tokens, per-key rate limiting, and audit labels.
- Reuse authenticated encrypted remote sessions and parallelize/caches multi-browser fanout to reduce repeated handshake roundtrips.
- Increase paged native-host batch size with extension-side byte budgeting to speed large tab listings safely.
- Point install output at public Chrome Web Store / Firefox AMO listings by default, with --dev preserving unpacked workflows.
- Share search-engine metadata between CLI and SDK and bump the package/extension version to 0.16.0.
- Cover the new security, pooling, paging, install, and fanout behavior with expanded Python and extension tests.

tests/conftest.py

@@ -8,45 +8,51 @@ They are automatically skipped if the native host socket is not reachable.
 import time
 import pytest
 from browser_cli.client import send_command, BrowserNotConnected
+from browser_cli.remote import pool as _remote_pool
 
 TEST_BROWSER_PROFILE = "testing"
 
+@pytest.fixture(autouse=True)
+def _clear_remote_pool():
+  """Close any pooled remote connections between tests so a connection opened
+  against one test's throwaway server can't leak into the next."""
+  yield
+  _remote_pool.close_all()
 
 @pytest.fixture(scope="session")
 def browser():
-    """Returns a connected send_command callable for the testing profile, or skips the test."""
-    try:
-        send_command("tabs.list", profile=TEST_BROWSER_PROFILE)
-    except (BrowserNotConnected, RuntimeError) as e:
-        pytest.skip(
-            f"Browser 'testing' not connected — start Brave/Chrome with the extension loaded for that profile ({e})"
-        )
+  """Returns a connected send_command callable for the testing profile, or skips the test."""
+  try:
+    send_command("tabs.list", profile=TEST_BROWSER_PROFILE)
+  except (BrowserNotConnected, RuntimeError) as e:
+    pytest.skip(
+      f"Browser 'testing' not connected — start Brave/Chrome with the extension loaded for that profile ({e})"
+    )
 
-    def _browser(command, args=None):
-        return send_command(command, args, profile=TEST_BROWSER_PROFILE)
-
-    return _browser
+  def _browser(command, args=None):
+    return send_command(command, args, profile=TEST_BROWSER_PROFILE)
 
+  return _browser
 
 @pytest.fixture()
 def http_tab(browser):
-    """Opens a dedicated http/https tab for the current test and returns its tab info."""
-    created = browser("navigate.open", {"url": "https://example.com", "background": True})
-    tab_id = created["id"]
+  """Opens a dedicated http/https tab for the current test and returns its tab info."""
+  created = browser("navigate.open", {"url": "https://example.com", "background": True})
+  tab_id = created["id"]
 
-    tab = None
+  tab = None
+  try:
+    for _ in range(30):
+      tabs = browser("tabs.list")
+      tab = next((t for t in tabs if t.get("id") == tab_id and t.get("url", "").startswith("http")), None)
+      if tab is not None:
+        break
+      time.sleep(0.1)
+    if tab is None:
+      pytest.skip("Dedicated http/https test tab did not finish loading")
+    yield tab
+  finally:
     try:
-        for _ in range(30):
-            tabs = browser("tabs.list")
-            tab = next((t for t in tabs if t.get("id") == tab_id and t.get("url", "").startswith("http")), None)
-            if tab is not None:
-                break
-            time.sleep(0.1)
-        if tab is None:
-            pytest.skip("Dedicated http/https test tab did not finish loading")
-        yield tab
-    finally:
-        try:
-            browser("tabs.close", {"tabId": tab_id})
-        except Exception:
-            pass
+      browser("tabs.close", {"tabId": tab_id})
+    except Exception:
+      pass