Add CLAUDE.md with FastMCP development guidelines

Establishes preference for in-memory transport when testing/investigating FastMCP servers, and recommends StreamableHttp over SSE for HTTP transport needs.

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Co-Authored-By: Claude <noreply@anthropic.com>

CLAUDE.md

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+# FastMCP Development Guidelines
+
+## Testing and Investigation
+
+### In-Memory Transport - Always Preferred
+
+When testing or investigating FastMCP servers, **always prefer the in-memory transport** unless you specifically need HTTP transport features. Pass a FastMCP server directly to a Client to eliminate separate processes and network complexity.
+
+```python
+# Create your FastMCP server
+mcp = FastMCP("TestServer")
+
+@mcp.tool
+def greet(name: str) -> str:
+    return f"Hello, {name}!"
+
+# Pass server directly to client - uses in-memory transport
+async with Client(mcp) as client:
+    result = await client.call_tool("greet", {"name": "World"})
+```
+
+### When to Use HTTP Transport
+
+Only use HTTP transport when testing network-specific features. Prefer StreamableHttp over SSE as it's the modern approach.
+
+```python
+# Only when network testing is required
+async with Client(transport=StreamableHttpTransport(server_url)) as client:
+    result = await client.ping()
+```