## Why

The management frontend has the required first-party navigation and a deeper AI provider page, but the console shell still behaves like a static page switcher with placeholder pages. This change turns `platform_web/` into a durable management console foundation for the next server-management workflows.

## What Changes

- Add a route-aware console shell with stable navigation state, page metadata, and accessible active-page behavior.
- Add richer first-party page surfaces for 首页、服务器管理、插件市场、用户管理、AI 提供商管理 using local-safe data until backend workflow APIs are introduced.
- Add frontend API types/client methods needed by shell pages for game plugins, server instances, and health/status summaries without exposing raw credentials or run internals.
- Add page/view contracts, schemas, and utilities that keep page components free of hidden shared business types.
- Add route/page tests, frontend build coverage, and a browser walkthrough for the console shell.

## Capabilities

### New Capabilities

- `platform-web-console-shell`: Defines the first-party frontend console shell, navigation behavior, page contracts, API client surface, and visual acceptance expectations for the management console.

### Modified Capabilities

- None.

## Impact

- `platform_web/`: app shell, route definitions, page registry, page contracts, API types/client methods, schemas/utilities, first-party pages, tests, and styling.
- OpenSpec artifacts and validation for the new `platform-web-console-shell` capability.
- No backend behavior changes are required in this change; pages may use existing API endpoints with local fallback data.