logiguard fork: GPUI xdg-activation keyboard-focus serial fix

Single-commit orphan branch: full zed-industries/zed @ 8c74db0 source tree
with a 3-file patch applied (no upstream history).

Patch (crates/gpui_linux/src/linux/wayland/):
  - serial.rs: add SerialKind::KeyboardEnter
  - client.rs: store wl_keyboard.enter serial; add latest_serial_of()
  - window.rs: activate() uses keyboard-enter serial (Mutter focus gate)

Mutter honors window activation only when the token carries the keyboard-
focus serial from wl_keyboard.enter; GPUI used a stale mouse-press serial.
See docs/tray-window-focus-wayland.md in logiguard.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

nix/livekit-libwebrtc/mkSystemLibraries.nix

@@ -0,0 +1,64 @@
+{
+  brotli,
+  fontconfig,
+  freetype,
+  harfbuzz,
+  icu,
+  jsoncpp,
+  libpng,
+  libwebp,
+  libxml2,
+  libxslt,
+  minizip,
+  ffmpeg_6,
+}:
+{
+  "brotli" = {
+    package = brotli;
+    path = "third_party/brotli/BUILD.gn";
+  };
+  "fontconfig" = {
+    package = fontconfig;
+    path = "third_party/fontconfig/BUILD.gn";
+  };
+  "freetype" = {
+    package = freetype;
+    path = "build/config/freetype/freetype.gni";
+  };
+  "harfbuzz-ng" = {
+    package = harfbuzz;
+    path = "third_party/harfbuzz-ng/harfbuzz.gni";
+  };
+  "jsoncpp" = {
+    package = jsoncpp;
+    path = "third_party/jsoncpp/BUILD.gn";
+  };
+  "icu" = {
+    package = icu;
+    path = "third_party/icu/BUILD.gn";
+  };
+  "libpng" = {
+    package = libpng;
+    path = "third_party/libpng/BUILD.gn";
+  };
+  "libwebp" = {
+    package = libwebp;
+    path = "third_party/libwebp/BUILD.gn";
+  };
+  "libxml" = {
+    package = libxml2;
+    path = "third_party/libxml/BUILD.gn";
+  };
+  "libxslt" = {
+    package = libxslt;
+    path = "third_party/libxslt/BUILD.gn";
+  };
+  "zlib" = {
+    package = minizip;
+    path = "third_party/zlib/BUILD.gn";
+  };
+  "ffmpeg" = {
+    package = ffmpeg_6;
+    path = "third_party/ffmpeg/BUILD.gn";
+  };
+}