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

docs_src/media/tutorial003.py

@@ -0,0 +1,20 @@
+from mcp_types import Icon
+
+from mcp.server import MCPServer
+
+LOGO = Icon(src="https://example.com/brand-kit.png", mime_type="image/png", sizes=["48x48"])
+PALETTE = Icon(src="https://example.com/palette.svg", mime_type="image/svg+xml", sizes=["any"])
+
+mcp = MCPServer("Brand kit", icons=[LOGO])
+
+
+@mcp.tool(icons=[PALETTE])
+def palette() -> list[str]:
+    """The brand colour palette as hex codes."""
+    return ["#1d4ed8", "#f59e0b", "#10b981"]
+
+
+@mcp.resource("brand://guidelines", icons=[LOGO])
+def guidelines() -> str:
+    """How to use the brand assets."""
+    return "Use the primary colour for calls to action."