build: support FFmpeg 7.x and 8.x; fix RPM spec GPU link deps

punktfunk-host builds unchanged against either FFmpeg 7.x (libavcodec 61) or 8.x
(libavcodec 62) — ffmpeg-sys-next auto-detects the system version, and the host's
ffmpeg FFI only touches long-stable APIs. Confirmed by building + running live on a
Bazzite F43 box (FFmpeg 7.1.3): full gamescope capture → zero-copy dmabuf→CUDA →
NVENC H.265 at 1280x720x60, p50 ~0.96 ms. Just doc/spec accuracy, no code change:

- encode/linux.rs + CLAUDE.md: drop the "FFmpeg 8 only" claim; note 7.x/8.x both work.
- rpm spec: add the missing zero-copy GPU build deps the link actually needs —
  pkgconfig(gl) + pkgconfig(gbm) (mesa) — and document that -lcuda needs libcuda.so at
  link time (NVIDIA host, or the CUDA toolkit stub on a headless COPR/koji builder).
  Tracked for a proper fix: make the cuda/gbm/GL FFI dlopen-based like khronos-egl so
  the RPM builds on a GPU-less host.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -158,7 +158,9 @@ cargo run -rp punktfunk-client-rs -- --mode 1280x720x120 --out /tmp/a.h265 --inp
 ```
 
 Pinned crate facts: `ashpd` 0.13 + `pipewire` 0.9 (must match ashpd's) + `ffmpeg-next` 8.x
-(system FFmpeg 8 / libavcodec 62). Env knobs: `PUNKTFUNK_VIDEO_SOURCE=virtual|portal`,
+(`ffmpeg-sys-next` auto-detects the system FFmpeg, so it builds against **FFmpeg 7.x/libavcodec 61
+or 8.x/libavcodec 62** — validated live on Ubuntu 26.04 (8) and Bazzite F43 (7.1); the zero-copy
+FFI also link-needs `libGL`/`libgbm`/`libcuda` at build time). Env knobs: `PUNKTFUNK_VIDEO_SOURCE=virtual|portal`,
 `PUNKTFUNK_COMPOSITOR=kwin|gamescope|mutter`, `PUNKTFUNK_ZEROCOPY=1`, `PUNKTFUNK_GAMESCOPE_APP=...`,
 `PUNKTFUNK_INPUT_BACKEND=...`, `PUNKTFUNK_PERF=1` (per-stage timing), `PUNKTFUNK_VIDEO_DROP=N` (FEC
 test), `PUNKTFUNK_FEC_PCT=N`.

crates/punktfunk-host/src/encode/linux.rs

@@ -1,4 +1,6 @@
-//! NVENC encoder via `ffmpeg-next` (binds the system FFmpeg 8.x / libavcodec 62).
+//! NVENC encoder via `ffmpeg-next` (binds the system FFmpeg — `ffmpeg-sys-next` auto-detects the
+//! installed version, so this builds against FFmpeg 7.x/libavcodec 61 *or* 8.x/libavcodec 62;
+//! validated live on Ubuntu 26.04 (FFmpeg 8) and Bazzite F43 (FFmpeg 7.1)).
 //!
 //! Input is a packed RGB/BGR CPU frame; `*_nvenc` accepts `rgb0`/`bgr0`/`rgba`/`bgra`
 //! directly and does the RGB→YUV conversion on the GPU, so the host stays off the

packaging/rpm/punktfunk.spec

@@ -47,9 +47,19 @@ BuildRequires:  pkgconfig(wayland-client)
 BuildRequires:  pkgconfig(xkbcommon)
 BuildRequires:  pkgconfig(opus)
 # FFmpeg dev headers with NVENC — from RPM Fusion (ffmpeg-devel), NOT ffmpeg-free.
+# Version-agnostic: ffmpeg-sys-next auto-detects the installed FFmpeg, so this builds
+# against FFmpeg 7.x (libavcodec 61, e.g. Fedora 43 / Bazzite) or 8.x (libavcodec 62).
 BuildRequires:  pkgconfig(libavcodec)
 BuildRequires:  pkgconfig(libavformat)
 BuildRequires:  pkgconfig(libavutil)
+# Zero-copy GPU path: src/zerocopy/ links libGL + libgbm (mesa) via hand-rolled FFI.
+BuildRequires:  pkgconfig(gl)
+BuildRequires:  pkgconfig(gbm)
+# It ALSO links the NVIDIA CUDA driver lib (-lcuda) via FFI, so libcuda.so must be present
+# at LINK time. A normal NVIDIA host (or Bazzite -nvidia) has it; a headless COPR/koji builder
+# without a GPU does NOT — point %build at the CUDA toolkit stub (…/stubs/libcuda.so) there,
+# e.g. `ln -s $(rpm -ql cuda-cudart-devel | grep stubs/libcuda.so | head -1) /usr/lib64/`.
+# (Proper fix tracked separately: make the cuda/gbm/GL FFI dlopen-based like khronos-egl.)
 
 # --- Runtime -----------------------------------------------------------------
 Requires:       pipewire