docs(mcp): name the console control as the UI does

8d3138a9 rewrote the MCP guide and introduced the "Connection test" wording,
which is also what turned the docs contract test red on master. That test has
since dropped its doc wording assertions (dae6bc6d), so this only keeps the
guide in line with the label both consoles use: mcp_test is "Test connection"
in the web console (channel/web/static/js/core/i18n.js:1461) and in the desktop
app (desktop/src/renderer/src/i18n.ts:1393).

docs/tools/mcp.mdx

@@ -10,7 +10,7 @@ CowAgent supports the [Model Context Protocol (MCP)](https://modelcontextprotoco
 The **MCP Tools** section of the Capabilities page in the **web console** and **desktop app** can add, edit, disable, and remove MCP servers without editing `mcp.json` by hand.
 
 - **Form or JSON**: fill in the form, or paste a standard `mcpServers` config in JSON mode (several servers at once), for example `{"mcpServers":{"fetch":{"command":"uvx","args":["mcp-server-fetch"]}}}`.
-- **Connection test**: checks that each server is reachable and lists its tools. Saving runs the same check first; if it fails, fix the config or choose **Save anyway** (for servers that require authorization after saving).
+- **Test connection**: checks that each server is reachable and lists its tools. Saving runs the same check first; if it fails, fix the config or choose **Save anyway** (for servers that require authorization after saving).
 - **Storage**: written to the current Agent's `mcp.json`, in the same format as Claude Desktop / Cursor.
 - **Immediate effect**: changes apply from the next message, with no restart.