fix(i18n): 修复 PROMPT_EXTENSIONS 元组声明、消除重复代码、优化锁策略

- fix: PROMPT_EXTENSIONS = (".prompt") 是字符串非元组，改为 (".prompt",)
- refactor: 将 extract_placeholders/format_template 统一到 loaders.py，
  消除 formatting.py、prompt_i18n.py、i18n_validate.py 三处重复
- perf: _get_catalog 和 load_prompt 改为双重检查锁定，I/O 不再阻塞其他线程
- perf: _log_once 使用独立 _warning_lock，不再与 _cache_lock 竞争
- fix: _scan_legacy_prompt_directory 添加 prompts_root 参数，修正 relative_to 语义
- refactor: 合并 _supported_prompt_files 两个变体为单函数 + recursive 参数
- docs: i18n.md 强化 repository-specific 校验策略标注，修正时间表述冗余
- fix: 验证脚本错误消息移除 Crowdin 暗示，标注为仓库级校验策略

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

src/common/i18n/formatting.py

@@ -2,28 +2,14 @@ from __future__ import annotations
 
 from datetime import date, datetime, time
 from decimal import Decimal
-from string import Formatter
 
 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, to_babel_locale
+from .loaders import DEFAULT_LOCALE, extract_placeholders, format_template, to_babel_locale
 
-FORMATTER = Formatter()
-
-
-def extract_placeholders(template: str) -> set[str]:
-    placeholders: set[str] = set()
-    for _, field_name, _, _ in FORMATTER.parse(template):
-        if not field_name:
-            continue
-        placeholders.add(field_name.split(".", maxsplit=1)[0].split("[", maxsplit=1)[0])
-    return placeholders
-
-
-def format_template(template: str, **kwargs: object) -> str:
-    return template.format(**kwargs)
+__all__ = ["extract_placeholders", "format_template"]
 
 
 def select_plural_category(locale: str, count: int | float | Decimal) -> str:

src/common/i18n/loaders.py

@@ -1,9 +1,12 @@
 from __future__ import annotations
 
 from pathlib import Path
+from string import Formatter
 
 import json
 
+_FORMATTER = Formatter()
+
 from .exceptions import (
     DuplicateTranslationKeyError,
     InvalidLocaleError,
@@ -122,3 +125,16 @@ def load_locale_catalog(locale: str, locales_root: Path | None = None) -> dict[s
                 )
             merged_translations[key] = value
     return merged_translations
+
+
+def extract_placeholders(template: str) -> set[str]:
+    placeholders: set[str] = set()
+    for _, field_name, _, _ in _FORMATTER.parse(template):
+        if not field_name:
+            continue
+        placeholders.add(field_name.split(".", maxsplit=1)[0].split("[", maxsplit=1)[0])
+    return placeholders
+
+
+def format_template(template: str, **kwargs: object) -> str:
+    return template.format(**kwargs)

src/common/i18n/manager.py

@@ -26,6 +26,7 @@ class I18nManager:
         self._locale_override: ContextVar[str | None] = ContextVar("maibot_locale", default=None)
         self._warning_cache: set[tuple[str, str, str]] = set()
         self._cache_lock = threading.RLock()
+        self._warning_lock = threading.Lock()
 
     def set_locale(self, locale: str) -> str:
         self._default_locale = normalize_locale(locale)
@@ -175,23 +176,26 @@ class I18nManager:
             if normalized_locale in self._catalog_cache:
                 return self._catalog_cache[normalized_locale]
 
-            try:
-                catalog = load_locale_catalog(normalized_locale, self._locales_root)
-            except I18nError as exc:
-                self._log_once(
-                    ("load_failed", normalized_locale, exc.__class__.__name__),
-                    logging.WARNING,
-                    "加载 locale '%s' 失败: %s",
-                    normalized_locale,
-                    exc,
-                )
-                catalog = {}
+        try:
+            catalog = load_locale_catalog(normalized_locale, self._locales_root)
+        except I18nError as exc:
+            self._log_once(
+                ("load_failed", normalized_locale, exc.__class__.__name__),
+                logging.WARNING,
+                "加载 locale '%s' 失败: %s",
+                normalized_locale,
+                exc,
+            )
+            catalog = {}
 
+        with self._cache_lock:
+            if normalized_locale in self._catalog_cache:
+                return self._catalog_cache[normalized_locale]
             self._catalog_cache[normalized_locale] = catalog
             return catalog
 
     def _log_once(self, cache_key: tuple[str, str, str], level: int, message: str, *args: object) -> None:
-        with self._cache_lock:
+        with self._warning_lock:
             if cache_key in self._warning_cache:
                 return
             self._warning_cache.add(cache_key)