Update flake.lock and add Cerebras LLM to Zed

Uncomment development package imports and include the `opencode` tool in
both system and Zed packages. Update librewolf’s search URL template and
refresh locked revisions, hashes, and timestamps in the flake.lock.

modules/core/packages/default.nix

@@ -4,7 +4,7 @@
   imports = [
     ./programs.nix
     ./clients.nix
-    # ./development.nix
+    ./development.nix
     ./gaming.nix
     ./multimedia.nix
     ./terminal.nix

modules/core/packages/development.nix

@@ -3,5 +3,7 @@
   environment.systemPackages = with pkgs; [
     # Learning & practice
     exercism
+    # AI coding
+    opencode
   ];
 }