docs: guidelines: initial laravel/mcp guidelines

Our documentation is great, so the guidelines don't need to be very detailed

Author: ashleyhindle

.ai/mcp/core.blade.php

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+## Laravel MCP
+- MCP, Model Context Protocol, is very new. You must use the `search-docs` tool to get documentation for how to write and test Laravel MCP servers, tools, resources, and prompts effectively.
+- MCP servers need to be registered with a route or handle in `routes/ai.php`. Typically you should start with `Mcp::web()` to register a HTTP streaming MCP server.
+- Servers are very testable - use the `search-docs` tool to find testing instructions.
+- Do not run `mcp:start`. This command hangs waiting for JSON RPC MCP requests.