MCP: the resource metadata URL should be derived from the full MCP server URL, not just the scheme+host.

Does this issue occur when all extensions are disabled?: Yes

- VS Code Version: 1.106.0 (or your current version)
- OS Version: All (OS Independent)

Bug Description:
When VS Code initializes an HTTP-based Model Context Protocol (MCP) server, the built-in MCP client fails to correctly discover metadata/OAuth resources because it forces a request to the server's root domain instead of matching the full configured path.

Specifically, when fetching `.well-known/oauth-protected-resource` or server metadata, VS Code strips the custom endpoint path and incorrectly queries `https://domain.com...` instead of honoring the explicit subpath endpoint layout (e.g., `https://domain.com...`), breaking connectivity for remote HTTP MCP servers hosted under sub-routes.

Steps to Reproduce:

1. Configure an HTTP remote MCP server inside `mcp.json` or `.vscode/mcp.json` using a URL that contains a subpath (e.g., `https://example.com`).
2. Reload the window or trigger an explicit connection/authentication sequence to the configured MCP server.
3. Observe the network or authentication trace logs. VS Code requests the metadata resources directly from the root domain (`https://example.com`) rather than appending it to the full MCP subpath route (`https://example.com`).
4. The connection fails with a 404 or a metadata mismatch error, preventing tools from loading in the chat or terminal.

Expected Behavior:
The VS Code native MCP client should preserve the full server path configuration or fallback sequentially to the precise path location before trying the bare root URL.