🔒 Security: ✅ LGTM

This pull request only removes build plumbing. It adds no secrets and does not touch authentication, authorization or input handling.

📖 AGENTS.md: ✅ LGTM

The edits to build/AGENTS.md and src/workerd/server/AGENTS.md match the removed _cross targets and no_build support.

📋 Code Quality: ✅ LGTM

No problems found in this cleanup.

• The repository head has no remaining references to workerd_cross, pyodide.capnp.bin_cross, no_build, target_run_under, prebuilt_binaries or QEMU. The search covered Bazel files, Markdown, scripts, JS and CI config.
• wd_test, wd_cli_test, py_wd_test and src/workerd/server/BUILD.bazel now use the plain //src/workerd/server:workerd and //src/pyodide:pyodide.capnp.bin targets.
• BuildSettingInfo is still used in build/wd_js_bundle.bzl, so that load is still needed.
• In kj_test and wd_rust_binary, target_compatible_with now defaults to None, and the value is still passed through correctly.

Nothing was built or run for this review. Whether every target still builds was not checked.

⚡ Performance: ✅ LGTM

No performance concerns.

📝 Documentation: ✅ LGTM

The comment edits in js-rpc-test.js and tail-worker-test-jsrpc.js describe the code as it is now, with QEMU dropped from the list of slow environments. This follows the repository's comment guidelines.