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/dev/flake.lock

@@ -0,0 +1,45 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1761236834,
+        "narHash": "sha256-+pthv6hrL5VLW2UqPdISGuLiUZ6SnAXdd2DdUE+fV2Q=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "d5faa84122bc0a1fd5d378492efce4e289f8eac1",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "treefmt-nix": "treefmt-nix"
+      }
+    },
+    "treefmt-nix": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      },
+      "locked": {
+        "lastModified": 1766000401,
+        "narHash": "sha256-+cqN4PJz9y0JQXfAK5J1drd0U05D5fcAGhzhfVrDlsI=",
+        "owner": "numtide",
+        "repo": "treefmt-nix",
+        "rev": "42d96e75aa56a3f70cab7e7dc4a32868db28e8fd",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "treefmt-nix",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

nix/dev/flake.nix

@@ -0,0 +1,10 @@
+{
+  description = "Private inputs for development purposes. These are used by the top level flake in the `dev` partition, but do not appear in consumers' lock files.";
+
+  inputs = {
+    treefmt-nix.url = "github:numtide/treefmt-nix";
+  };
+
+  # This flake is only used for its inputs.
+  outputs = { ... }: { };
+}