webrtc-sys: forward-declare PeerContext as struct (fixes 4x LNK2019 on windows-msvc)

[wcares]

Summary

webrtc-sys/include/livekit/jsep.h forward-declares class PeerContext;, but PeerContext is a cxx shared type defined on the Rust side as pub struct PeerContext (src/peer_connection.rs), so cxx emits struct PeerContext everywhere it generates C++.

Under the MSVC ABI (clang-cl / cl), the class vs struct tag is part of the mangled name, so rust::Box<class PeerContext> (from jsep.cpp, which includes jsep.h) and rust::Box<struct PeerContext> (from the cxx-generated peer_connection.cc) mangle to different symbols → 4 unresolved externals at link on x86_64-pc-windows-msvc:

LNK2019: unresolved external symbol ... rust::Box<PeerContext>::drop / ::from_raw / ...

GCC/Clang on Linux/macOS use the Itanium ABI, which ignores the class/struct tag in mangling, so this never surfaces there — only the MSVC ABI is affected. Verified identical in webrtc-sys 0.3.21 and 0.3.32.

Fix (1 word)

-class PeerContext;
+struct PeerContext;

jsep.h is the only place in the crate that tags PeerContext as class; every other reference uses rust::Box<PeerContext> (untagged) and the cxx bridge declares it struct. Making the forward declaration struct makes the tag consistent crate-wide. No-op on Linux/macOS; fixes the link on windows-msvc.

Verification

With this change applied (via [patch.crates-io]), omnynet-agent links clean with the livekit-av feature ON on x86_64-pc-windows-msvc (clang-cl), in combination with +crt-static for the libwebrtc /MT prebuilt, and runtime-connects to a LiveKit room (rust SDK 0.7.42).

Closes the windows-msvc build failure tracked in #1154.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}