fix: harden IPC, screenshot, paging, and tab filter error handling

- tabs.py: validate screenshot data URL prefix and catch binascii.Error
  instead of silently writing a zero-byte file or crashing with a raw traceback
- serve.py: add 30 s recv timeout on client connections to prevent unbounded
  thread accumulation; use hmac.compare_digest for constant-time token check
- native_host.py: bind Unix socket before _registry_add to eliminate the
  window where the registry points to an unbound path; cap paging loop at
  ceil(10000/PAGE_SIZE) iterations to guard against a misbehaving extension;
  remove dead no-hello fast-path queue that was registered but never consumed
- __init__.py: narrow _apply_tab_filter except to (AttributeError, TypeError)
  so broken filter functions raise instead of silently returning wrong results

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

browser_cli/__init__.py

@@ -685,8 +685,8 @@ class BrowserCLI:
 
         try:
             transformed = filter_fn(tabs)
-        except Exception:
-            transformed = None
+        except (AttributeError, TypeError):
+            return [tab for tab in tabs if filter_fn(tab)]
 
         if isinstance(transformed, list):
             return transformed