feat: add The Stall MCP preset (210 pay-per-call x402 data tools via SSE)

[KyleMillion]

Summary

Adds The Stall to the MCP preset registry — a production x402 capability chassis with 210 pay-per-call data tools for AI agents.

What is The Stall?

• 210 MCP tools covering finance, crypto/DeFi, macro indicators, prediction markets, OSINT, weather, flight tracking, and more
• x402 payment — agents pay per call in USDC on Base mainnet; no API key or account required
• SSE transport — fully compatible with the McpSsePreset schema at https://the-stall.intuitek.ai/sse
• Free MCP endpoint — POST /mcp is available at no cost for tool discovery

Preset entry

{
  id: 'the-stall',
  name: 'The Stall',
  transport: 'sse',
  url: 'https://the-stall.intuitek.ai/sse',
  toolPrefix: 'stall_',
  docsUrl: 'https://the-stall.intuitek.ai',
  timeout: 30_000,
}

Live verification

# SSE endpoint
curl -H "Accept: text/event-stream" https://the-stall.intuitek.ai/sse
# → event: endpoint
# → data: /messages?sessionId=<uuid>

# Health check
curl https://the-stall.intuitek.ai/health
# → {"ok":true,"network":"base","capabilities":[...210 tools...]}

Checklist

• No API keys or secrets embedded (x402 payment is autonomous — no caller credential needed)
• id is stable kebab-case: the-stall
• toolPrefix is unique: stall_
• Transport is sse (schema-compatible)
• Live SSE endpoint verified before filing this PR

[KyleMillion]

Hi — following up on this PR. The Stall now supports SSE transport (added in v4.64.0) which should satisfy the preset requirements. Happy to adjust anything if needed. Thanks for the review!