GHSA-x4mq-m75f-mx8m: Delegate functions are missing `Send` bound

The vulnerability manifests in delegate handler constructors across multiple Windows API modules where FnMut parameters lacked Send bounds. The commit diff shows systematic addition of ::core::marker::Send to all handler generics. High confidence comes from: 1) Vulnerability description specifically calls out delegate handlers 2) Commit modifies 50+ handler implementations 3) CWE-820 directly relates to missing synchronization primitives 4) Example in GHSA shows TypedEventHandler was vulnerable 5) Windows API documentation for free-threaded handlers requires thread-safe callbacks.