Pin the template's zisk.nix input to the blake3-precompile branch

The template's fork-based zisk-sdk/ziskos deps need the dev shell tools
built from the same fork rev; following the default branch would break if
main tracks upstream.

Author: samuelburnham

templates/sha_hasher/flake.nix

@@ -15,7 +15,7 @@
     flake-parts.follows = "zisk/flake-parts";
 
     zisk = {
-      url = "github:argumentcomputer/zisk.nix";
+      url = "github:argumentcomputer/zisk.nix/blake3-precompile";
     };
   };