opencode: fix missing tree-sitter-htesyypn.node module runtime error

Added `tree-sitter` to `buildInputs` to fix runtime error

```sh
ResolveMessage: Cannot find module '/$bunfs/root/../../../tree-sitter-
htesyypn.node' from '/$bunfs/root/opencode'
```

when command `/init` is executed when the project doesn't yet contain an
`AGENTS.md` file.

Closes #430293

pkgs/by-name/op/opencode/package.nix

@@ -7,6 +7,7 @@
   models-dev,
   nix-update-script,
   testers,
+  tree-sitter,
   writableTmpDirAsHomeHook,
 }:
 
@@ -107,6 +108,8 @@ stdenvNoCC.mkDerivation (finalAttrs: {
     outputHashMode = "recursive";
   };
 
+  buildInputs = [ tree-sitter ];
+
   nativeBuildInputs = [
     bun
     models-dev