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.

browser_cli/commands/__init__.py

@@ -31,6 +31,66 @@ def gentle_mode_option(help_text: str):
     help=help_text,
   )
 
+def command_policy_options(fn):
+  """Reusable raw-command safety flags for /command-like entry points."""
+  fn = click.option(
+    "--allow-all",
+    is_flag=True,
+    help="Allow every command (equivalent to --allow-read-page --allow-control --allow-dangerous --allow-keys)",
+  )(fn)
+  fn = click.option(
+    "--allow-keys",
+    is_flag=True,
+    help="Allow key-management commands (list/trust authorized keys over --remote)",
+  )(fn)
+  fn = click.option(
+    "--allow-dangerous",
+    is_flag=True,
+    help="Allow high-risk commands such as dom.eval, storage.*, screenshots",
+  )(fn)
+  fn = click.option(
+    "--allow-control",
+    is_flag=True,
+    help="Allow browser-control commands such as nav.*, tabs.close, dom.click",
+  )(fn)
+  fn = click.option(
+    "--allow-read-page",
+    is_flag=True,
+    help="Allow page-content read commands such as extract.* and dom.text",
+  )(fn)
+  return fn
+
+def command_policy_from_options(*, allow_read_page: bool, allow_control: bool, allow_dangerous: bool, allow_keys: bool = False, allow_all: bool = False):
+  """Build a CommandPolicy from shared raw-command safety flags."""
+  from browser_cli.command_security import CommandPolicy
+
+  if allow_all:
+    return CommandPolicy.unrestricted()
+  return CommandPolicy(
+    allow_read_page=allow_read_page,
+    allow_control=allow_control,
+    allow_dangerous=allow_dangerous,
+    allow_keys=allow_keys,
+  )
+
+def command_categories_from_options(*, allow_read_page: bool, allow_control: bool, allow_dangerous: bool, allow_keys: bool = False, allow_all: bool = False):
+  """Convert the shared --allow-* flags into a category list, or None if none were set.
+
+  None means "no explicit policy" — the key falls back to the server-wide default.
+  """
+  if allow_all:
+    return ["all"]
+  cats = []
+  if allow_read_page:
+    cats.append("read-page")
+  if allow_control:
+    cats.append("control")
+  if allow_dangerous:
+    cats.append("dangerous")
+  if allow_keys:
+    cats.append("keys")
+  return cats or None
+
 def print_counts(result, noun: str, *, single_suffix: str = "") -> None:
   """Render a count result.