Fix flacks like https://github.com/zed-industries/zed/actions/runs/33546906778/job/99987145940?pr=63573 `test_extension_store_with_test_extension` gives the extension builder `target` as its cache at `crates/extension_host/src/extension_store_test.rs:801`. `install_dev_extension` performs a real extension and grammar build at `crates/extension_host/src/extension_host.rs:1139`. When `target/wasi-sdk` is absent (e.g. after `target/` cleanup), the builder downloads and extracts it at `crates/extension/src/extension_builder.rs:511`. In the failed run, downloading and extracting the SDK consumed 59 seconds, grammar compilation began at 60 seconds, and the timeout fired immediately. Release Notes: - N/A