TEST BUILD — root-cause fix for the AMD/AMF hang (not yet on master)

Candidate fix for ApolloVibe#2, held on a branch pending confirmation.

Upstream Sunshine commit 02036920, "build(deps): Update to FFmpeg 8.0 branch (#4143)", changed two things in one commit: it added a drain to ~avcodec_encode_session_t() and bumped third-party/build-deps from 94369e63 to a21ef2e3. The drain was written for FFmpeg 8.0.

Apollo merged the source half and kept its own older build-deps pin. The version strings prove it — ours and upstream Apollo carry Windows FFmpeg "6400860"; Sunshine after that commit carries "git-2025-08-09-7eaa0f7". On AMD/AMF, avcodec_send_frame(ctx, nullptr) then never returns.

This build removes the drain, restoring Apollo v0.4.6 behaviour. It moves no data — the packets were discarded on the next line.

Built from a358bba8 on fix/no-encoder-flush-on-destroy. sunshine.exe SHA256 begins aa16f9bcb0c9dcc3.

⚠️ Pre-release on purpose. The properly aligned fix is bumping build-deps, which belongs upstream.