Rebuild the docs around tested examples; shrink README.v2.md to a pitch (#2978)

docs_src/prompts/tutorial002.py

@@ -0,0 +1,20 @@
+from mcp.server import MCPServer
+from mcp.server.mcpserver.prompts.base import AssistantMessage, Message, UserMessage
+
+mcp = MCPServer("Code Helper")
+
+
+@mcp.prompt()
+def review_code(code: str) -> str:
+    """Review a piece of code."""
+    return f"Please review this code:\n\n{code}"
+
+
+@mcp.prompt()
+def debug_error(error: str) -> list[Message]:
+    """Start a debugging conversation."""
+    return [
+        UserMessage("I'm seeing this error:"),
+        UserMessage(error),
+        AssistantMessage("I'll help debug that. What have you tried so far?"),
+    ]