fix(nix): refresh upstream Nix pins for 26.715.31251 (ilysenko#1065)

Refreshed Codex.dmg SRI hash to sha256-hs3FKrLBT42VNYCRIbJRLpuJE4/qr6asaXuuhxDqGds= and synced codexVersion / electronVersion / native-module pins to the current upstream DMG.

Verified all ChatGPT Desktop Nix package outputs against the refreshed DMG.

Source-Main-SHA: d1d29e8

Upstream-DMG-SHA256: 86cdc52ab2c14f8d9535809121b2512e9b89138feaafa6ac697bae8710ea19db

Co-authored-by: codex-dmg-hash-bot <actions@github.com>

Author: github-actions[bot]

flake.nix

@@ -94,10 +94,10 @@
 
         codexDmg = pkgs.fetchurl {
           url = "https://persistent.oaistatic.com/codex-app-prod/ChatGPT.dmg";
-          hash = "sha256-/0WRUJkWEgB1SScNLSjF54zsa9asIAp62l7WwDE2m4c=";
+          hash = "sha256-hs3FKrLBT42VNYCRIbJRLpuJE4/qr6asaXuuhxDqGds=";
         };
 
-        codexVersion = "26.715.21425";
+        codexVersion = "26.715.31251";
         electronVersion = "42.3.0";
         electronPlatform =
           {