Core fix: now check will run against current branch most recent commit and will be triggered by nix file outside of project root

Author: RyanPrussin

.github/workflows/check-flake.yml

@@ -1,8 +1,8 @@
 name: Check Nix flake
 on:
-  pull_request_target:
+  pull_request:
     paths:
-      - '*.nix'
+      - '**.nix'
       - flake.lock
   push:
     branches: