refactor: reorganize client transport and extension internals

- Split client, native, remote, serve, markdown, and SDK internals into focused packages with direct imports.
- Move local and remote transport framing/protocol helpers behind clearer module boundaries.
- Break up the extension injected DOM logic into a separate content dispatch bundle and dedicated content modules.
- Add explicit client handling for passive remote discovery without noisy PQ warnings.
- Keep behavior covered with updated unit, integration, and extension tests.

browser_cli/sdk/__init__.py

@@ -5,6 +5,7 @@ client (``b.tabs``, ``b.dom``, ``b.session``, ...), mirroring the command groups
 in the browser extension.
 """
 from browser_cli.sdk.browser_data import CookiesNS, StorageNS
+from browser_cli.sdk.decorators import DecoratorsNS
 from browser_cli.sdk.dom import DomNS, ExtractNS, PageNS
 from browser_cli.sdk.extension import ExtensionNS
 from browser_cli.sdk.groups import GroupsNS
@@ -14,6 +15,22 @@ from browser_cli.sdk.session import SessionNS
 from browser_cli.sdk.tabs import TabsNS
 from browser_cli.sdk.windows import WindowsNS
 
+NAMESPACE_SPECS = (
+    ("nav", NavigationNS),
+    ("tabs", TabsNS),
+    ("groups", GroupsNS),
+    ("windows", WindowsNS),
+    ("dom", DomNS),
+    ("extract", ExtractNS),
+    ("page", PageNS),
+    ("storage", StorageNS),
+    ("cookies", CookiesNS),
+    ("session", SessionNS),
+    ("perf", PerfNS),
+    ("extension", ExtensionNS),
+)
+NAMESPACE_NAMES = tuple(name for name, _ in NAMESPACE_SPECS)
+
 __all__ = [
     "NavigationNS",
     "TabsNS",
@@ -27,4 +44,7 @@ __all__ = [
     "SessionNS",
     "PerfNS",
     "ExtensionNS",
+    "DecoratorsNS",
+    "NAMESPACE_SPECS",
+    "NAMESPACE_NAMES",
 ]