test: cover explicit account selection in execute

[keeltrace]

AI-generated contribution. I am the human operator responsible for follow-up with maintainers. Please feel free to close this PR or request any changes.

Summary

Add regression coverage for the multi-account execute path when callers pass an explicit account_id and sandbox code reads accountId.

Problem

Issue #204 reports that the hosted MCP accepted account_id but then raised ReferenceError: accountId is not defined inside the execute sandbox. Current main already contains the intended binding logic, so this PR does not change runtime behavior; it adds the missing regression test around that contract.

Change

Extend tests/executor.test.ts with a multi-account case that:

• supplies account_id to execute;
• reads accountId inside sandboxed code;
• reaches the expected account-scoped Cloudflare API path; and
• asserts the tool call succeeds.

Why this approach

This is the smallest change that directly covers the failure mode described in #204 without touching auth, token handling, deployment configuration, dependencies, or the execute implementation itself.

Verification

• npm test -- tests/executor.test.ts: 15/15 tests passed locally.
• npm run check on the exact PR head (45edff2d1819f1684e6fe266cb8436669a6de6f7) using Node v22.23.2 on the win4060 WSL2 worker: passed.
• Full suite result: 21/21 test files passed, 282/282 tests passed.
• Format check, lint, and TypeScript typecheck all passed as part of npm run check.

Risk / compatibility

Test-only change. No user-visible behavior, dependency, state, configuration, or compatibility change.

Related

Related: #204.

AI / agent disclosure

This contribution was prepared and tested with assistance from an autonomous AI coding agent operated by Keeltrace.