docs: correct locale activation return type and thread scope

Document the translation object returned by activate() and clarify that activation and deactivation apply to the calling thread.

Prepared with AI assistance (OpenAI Codex).

Author: raghav-sharma-ai

src/humanize/i18n.py

@@ -59,15 +59,16 @@ def activate(
 ) -> gettext_module.NullTranslations:
     """Activate internationalisation.
 
-    Set `locale` as current locale. Search for locale in directory `path`.
+    Set `locale` as the current locale for the calling thread. Search for locale
+    in directory `path`.
 
     Args:
         locale (str | None): Language name, e.g. `en_GB`. If `None`, defaults to no
             translation. Similar to calling ``deactivate()``.
         path (str | pathlib.Path): Path to search for locales.
 
     Returns:
-        dict: Translations.
+        gettext.NullTranslations: Translation object for the selected locale.
 
     Raises:
         FileNotFoundError: If humanize cannot find the locale folder.
@@ -93,7 +94,7 @@ def activate(
 
 
 def deactivate() -> None:
-    """Deactivate internationalisation."""
+    """Deactivate internationalisation for the calling thread."""
     _CURRENT.locale = None