feat: add mcp client approval callbacks

[parvahuja]

Summary

• Add an optional payment approval callback to wrapped MCP client tool calls
• Support callTool(null, params) for explicit automatic payment
• Add type and runtime coverage for approval, denial, and explicit auto-pay flows

Context

Agent SDK integrations often need a human-in-the-loop step before an agent pays for a tool call. This keeps the existing callTool(params, options) API intact and adds an overload for approval-aware calls.

Usage

Before:

const paidMcp = McpClient.wrap(mcpClient, { methods })

const result = await paidMcp.callTool({
  name: "premium_tool",
  arguments: toolArgs,
})

After:

const result = await paidMcp.callTool(approvePayment, {
  name: "premium_tool",
  arguments: toolArgs,
})

Use paidMcp.callTool(null, params) to make the automatic-payment choice explicit.

Validation

• pnpm check
• pnpm check:types
• VITE_NODE_ENV=unit pnpm test --project node src/mcp-sdk/client/McpClient.unit.test.ts

Note: pnpm check:types still emits existing ox/viem Tempo channel bundler warnings, but exits successfully.

[brendanjryan]

👍