Increment 2: wires the host-call machinery into the running FFI thread so a
host answer (delivered from any thread) resolves the chronos Future an awaiting
handler is blocked on.
- FFICompletionQueue (ffi_host.nim): a GC-free intrusive queue. host_complete
pushes c_malloc'd nodes from any thread; the FFI thread drains, copies the
payload into GC memory, completes the future by token, and frees the node.
- FFIContext gains hostRegistry / pendingTable / completionQueue, init'd and
deinit'd alongside the event registry.
- completeHostCall parks the answer and fires the EXISTING reqSignal — no second
ThreadSignalPtr needed; the loop drains completions every iteration, on the
loop thread (chronos single-thread invariant).
- On shutdown the loop failAllPendings first, so a handler awaiting a host
answer that never arrives can't hang the allFutures(pending) drain.
4 new queue unit tests (10 total) pass under orc+refc; the 19 ffi_context
integration tests stay green.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
* protect against mem leak in case of failures sending requests to ffi thread
* better cleanup if failures in createFFIContext
* avoid dangling cstring in handleRes under ARC/ORC
* better resource cleanup in destroyFFIContext
* invoke onNotResponding if failure in destroyFFIContext
* correct seq copy in alloc
* make sure the lock is init before cleanUpResources
* better possible exception handling in processReq
* guard allocSharedSeq if given seq is empty
* enhance error handling in ffi_context
* add new tests and some corrections
