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

docs_src/elicitation/tutorial002.py

@@ -0,0 +1,24 @@
+from mcp.server import MCPServer
+from mcp.server.mcpserver import Context
+
+mcp = MCPServer("Bistro")
+
+
+@mcp.tool()
+async def pay_deposit(booking_id: str, ctx: Context) -> str:
+    """Take the deposit that confirms a booking."""
+    result = await ctx.elicit_url(
+        message="A 20 EUR deposit confirms your booking.",
+        url=f"https://pay.example.com/deposit/{booking_id}",
+        elicitation_id=f"deposit-{booking_id}",
+    )
+    if result.action == "accept":
+        return "Complete the payment in your browser."
+    return "No deposit taken. The booking expires in one hour."
+
+
+@mcp.tool()
+async def confirm_deposit(booking_id: str, ctx: Context) -> str:
+    """Record a payment reported by the payment provider."""
+    await ctx.session.send_elicit_complete(f"deposit-{booking_id}")
+    return f"Deposit received for booking {booking_id}."