feat(mcp): friendly UI message when stdio MCP refused by Box state

Previously the MCP detail dialog dumped the raw RuntimeError text from
``_init_stdio_python_server`` — English-only, prefixed with "Failed
after 4 attempts", and exposing internal config names. The retry
wrapper also kept retrying a refusal that is deterministically going
to fail again, polluting logs.

Replace the raw text with a structured signal:

- New ``MCPSessionErrorPhase.BOX_UNAVAILABLE`` enum value. The stdio
  refusal path sets it before raising and uses a short opaque
  discriminator (``box_disabled_in_config`` / ``box_unavailable``) as
  the message body — never user-facing
- ``_lifecycle_loop_with_retry`` short-circuits on
  ``BOX_UNAVAILABLE``: surfaces the error immediately, no retries,
  no "Failed after N attempts" prefix. Silences the warning storm
  seen during smoke-testing
- ``MCPServerRuntimeInfo`` (TS type) now declares ``error_phase``,
  ``retry_count``, ``box_session_id``, ``box_enabled`` to match what
  the backend already returns in get_runtime_info_dict()
- Both MCP detail forms (``mcp/components/mcp-form/MCPForm.tsx`` and
  ``plugins/mcp-server/mcp-form/MCPFormDialog.tsx``) detect
  ``error_phase === 'box_unavailable'`` and render a two-line
  localized notice: state line ("Box disabled / unreachable") plus
  remediation line ("enable Box or switch to http/sse")
- 8 locale files (en/zh-Hans/zh-Hant/ja/ru/vi/th/es) get
  ``mcp.boxDisabledStdioRefused``, ``mcp.boxUnavailableStdioRefused``,
  ``mcp.boxStdioRefusedSuggestion``

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

web/src/i18n/locales/ru-RU.ts

@@ -748,6 +748,12 @@ const ruRU = {
     connectionSuccess: 'Подключение успешно',
     connectionFailed: 'Не удалось подключиться, проверьте URL',
     connectionFailedStatus: 'Ошибка подключения',
+    boxDisabledStdioRefused:
+      'MCP-серверы в режиме stdio требуют песочницу Box, которая отключена в конфигурации (box.enabled = false).',
+    boxUnavailableStdioRefused:
+      'MCP-серверы в режиме stdio требуют песочницу Box, которая сейчас недоступна.',
+    boxStdioRefusedSuggestion:
+      'Включите Box (box.enabled = true) и убедитесь, что среда работает, либо переключите этот сервер в режим http/sse.',
     toolsFound: 'инструментов',
     unknownError: 'Неизвестная ошибка',
     noToolsFound: 'Инструменты не найдены',