[QuantumExplorer]

Fixes #106.

Problem

BodyStream holds JS objects (the fetch body stream, the AbortController and the timeout closure), which belong to the thread that created them. Its unsafe impl Send applies to every target. That is fine on single-threaded wasm, but with wasm threads (target_feature = "atomics") a ResponseBody can be moved to another worker, where polling or dropping it touches JS handles that belong to another thread.

Fix

With target_feature = "atomics", BodyStream records the thread that created it, panics if it is polled on another thread, and leaks its JS objects if it is dropped on another thread. Without atomics nothing changes: the new code is all behind cfg.

The Send and Sync impls stay, with a comment on why they hold. tonic needs Send, and Sync was already sound, because &BodyStream gives no access to the JS objects. Removing Send under atomics would also be sound, but builds with wasm threads would then stop compiling, since tonic would reject ResponseBody.

Before and after

Build and use	Before	After
wasm32 without threads	Send, sound (one thread)	unchanged
wasm32 with atomics, body polled on the thread that created it	works	works
wasm32 with atomics, body polled on another thread	uses another thread's JS handles	panics: "a ResponseBody must be polled on the thread that created it"
wasm32 with atomics, body dropped on another thread	uses another thread's JS handles	the JS objects are leaked

Tests

There is no automated test, since exercising this needs a multi-threaded wasm app. I checked that the crate builds and passes clippy both ways: as usual, and with RUSTFLAGS="-C target-feature=+atomics,+bulk-memory" cargo +nightly clippy --target wasm32-unknown-unknown -Z build-std=panic_abort,std.

cargo fmt --check, cargo clippy --all-targets -- -D warnings, cargo clippy --target wasm32-unknown-unknown -- -D warnings and cargo test are clean, and the browser suite in test-suite/simple passes in headless Chrome 153.

This is one of 14 PRs from the review asked for in #97. They are independent, and all 14 also merge together cleanly; with all of them merged, both browser suites (test-suite/simple and test-suite/gzip) pass.

🤖 Generated with Claude Code