Fix direct sandbox hosts in Python and Go for v0.1.7

[muxx]

Summary

• Align Python and Go direct sandbox host derivation with the JavaScript SDK when the configured proxy URL is https://sandbox.agentbox-runtime.ru.
• Preserve explicit proxy ports and custom proxy host behavior, with regression tests for both languages.
• Include the existing JavaScript CommandNotFoundError export in the generated SDK reference.
• Prepare all six public packages and the reference manifest for v0.1.7.

Verification

• pnpm format:check, pnpm lint, pnpm typecheck, pnpm test
• make go-check (including race and coverage: core 90.7%, Code Interpreter 90.4%)
• make generate twice; the second run left the working tree clean
• node scripts/check-release-versions.mjs v0.1.7
• ./scripts/build-release.sh, node scripts/check-public-artifacts.mjs release, ./scripts/test-release-artifacts.sh
• ./scripts/test-release-runtime.sh against the local full KVM runtime: JavaScript, CLI, Python sync/async, Go, and Code Interpreter passed

After merge, the maintainer will create the matching packages/go-sdk/v0.1.7 and v0.1.7 tags as described in RELEASING.md.