chore(flake): point opencode to sst/opencode/dev and refresh flake.lock

Point opencode input to the official sst/opencode dev branch (PR #3924 merged) and refresh flake.lock so pinned revisions and narHashes are updated across inputs (nixpkgs, nixpkgs-darwin, nixpkgs-unstable, nixvim, NUR, opencode).

Refs anomalyco/opencode#3924

Author: Andrew Austin

flake.lock

@@ -37,9 +37,9 @@
       inputs.nixpkgs.follows = "nixpkgs-unstable";
     };
 
-    # OpenCode flake (testing PR #3924)
+    # OpenCode flake (official - PR #3924 merged)
     opencode = {
-      url = "github:Alb-O/opencode/nix-support";
+      url = "github:sst/opencode/dev";
       inputs.nixpkgs.follows = "nixpkgs-unstable";
     };