fix(i18n): tighten prompt and catalog fallback handling

src/common/i18n/formatting.py

@@ -7,9 +7,7 @@ from babel import Locale
 from babel.dates import format_datetime as babel_format_datetime
 from babel.numbers import format_decimal as babel_format_decimal
 
-from .loaders import DEFAULT_LOCALE, extract_placeholders, format_template, to_babel_locale
-
-__all__ = ["extract_placeholders", "format_template"]
+from .loaders import DEFAULT_LOCALE, to_babel_locale
 
 
 def select_plural_category(locale: str, count: int | float | Decimal) -> str:

src/common/i18n/manager.py

@@ -10,7 +10,8 @@ import os
 import threading
 
 from .exceptions import I18nError, InvalidLocaleError
-from .formatting import format_template, select_plural_category
+from .formatting import select_plural_category
+from .loaders import format_template
 from .loaders import DEFAULT_LOCALE, TranslationValue, get_locales_root, load_locale_catalog, normalize_locale
 
 logger = logging.getLogger("maibot.i18n")
@@ -134,7 +135,7 @@ class I18nManager:
             return format_template(template, **kwargs)
         except Exception as exc:
             logger.error("翻译 key '%s' 格式化失败: %s", key, exc)
-            return template or key
+            return template
 
     def _get_translation_value(self, key: str, locale: str | None) -> tuple[TranslationValue | None, str]:
         target_locale = self._resolve_locale(locale)
@@ -198,7 +199,7 @@ class I18nManager:
                 normalized_locale,
                 exc,
             )
-            catalog = {}
+            return {}
 
         with self._cache_lock:
             if normalized_locale in self._catalog_cache:

src/prompt/prompt_manager.py

@@ -181,8 +181,10 @@ class PromptManager:
         self,
         prompt: Prompt,
         recursive_level: int = 0,
-        additional_construction_function_dict: dict[str, Callable[[str], str | Coroutine[Any, Any, str]]] = {},  # noqa: B006
+        additional_construction_function_dict: dict[str, Callable[[str], str | Coroutine[Any, Any, str]]] | None = None,
     ) -> str:
+        if additional_construction_function_dict is None:
+            additional_construction_function_dict = {}
         prompt.template = prompt.template.replace("{{", _LEFT_BRACE).replace("}}", _RIGHT_BRACE)
         if recursive_level > 10:
             raise RecursionError("递归层级过深，可能存在循环引用")
@@ -191,11 +193,11 @@ class PromptManager:
         for field_name in field_block:
             if field_name in self.prompts:
                 nested_prompt = self.get_prompt(field_name)
-                additional_construction_function_dict |= prompt.prompt_render_context
+                merged_context = additional_construction_function_dict | prompt.prompt_render_context
                 rendered_fields[field_name] = await self._render(
                     nested_prompt,
                     recursive_level + 1,
-                    additional_construction_function_dict,
+                    merged_context,
                 )
             elif field_name in prompt.prompt_render_context:
                 # 优先使用内部构造函数