Include x402 EVM extra so signer imports resolve in clean env

x402.mechanisms.evm.signers imports web3 at module load. Without the
evm extra, `from x402.mechanisms.evm.signers import EthAccountSigner`
raises ImportError in a fresh notebook environment. Switching to
x402[httpx,evm] also makes the standalone eth-account pin redundant.

Author: hypeprinter007-stack

examples/agents_sdk/paying_apis_with_x402.ipynb

@@ -58,11 +58,10 @@
    "source": [
     "## Setup\n",
     "\n",
-    "Install three packages:\n",
+    "Install two packages:\n",
     "\n",
     "- [`openai-agents`](https://github.com/openai/openai-agents-python) — the Agents SDK\n",
-    "- [`x402[httpx]`](https://pypi.org/project/x402/) — official Python client for the x402 protocol, with an `httpx`-based HTTP wrapper\n",
-    "- [`eth-account`](https://eth-account.readthedocs.io/) — for constructing a Base signer from a private key"
+    "- [`x402[httpx,evm]`](https://pypi.org/project/x402/) — official Python client for the x402 protocol. The `httpx` extra adds the `httpx`-based HTTP wrapper; the `evm` extra pulls in `eth-account` + `web3`, required by the Base signer."
    ]
   },
   {
@@ -79,7 +78,7 @@
    },
    "outputs": [],
    "source": [
-    "%pip install --quiet \"openai-agents>=0.17.0\" \"x402[httpx]>=2.10.0\" \"eth-account>=0.13.0\""
+    "%pip install --quiet \"openai-agents>=0.17.0\" \"x402[httpx,evm]>=2.10.0\""
    ]
   },
   {