chore(nix->guix): delete Nix estate-wide (#138) (#49)

Automated sweep to eradicate Nix from the estate as Guix is now the sole
reproducible environment.

Author: hyperpolymath

.envrc

@@ -14,7 +14,6 @@ fi
 
 # Load Nix flake if flake.nix exists
 if has nix && [ -f flake.nix ]; then
-  use flake
 fi
 
 # Project environment variables

.github/workflows/governance.yml

@@ -31,4 +31,4 @@ permissions:
 
 jobs:
   governance:
-    uses: hyperpolymath/standards/.github/workflows/governance-reusable.yml@7fdc2705df74b4e352d2a1cde3e87a5923fdf329
+    uses: hyperpolymath/standards/.github/workflows/governance-reusable.yml@7fdc2705df74b4e352d2a1cde3e87a5923fdf329

.github/workflows/hypatia-scan.yml

@@ -26,4 +26,4 @@ permissions:
 jobs:
   hypatia:
     uses: hyperpolymath/standards/.github/workflows/hypatia-scan-reusable.yml@7fdc2705df74b4e352d2a1cde3e87a5923fdf329
-    secrets: inherit
+    secrets: inherit

.github/workflows/proof-gate.yml

@@ -28,7 +28,6 @@ jobs:
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
-      - uses: cachix/install-nix-action@a49548c11d9846ad46ecc0115273879b045f001c # v31.10.7
 
       - name: Run proof gate
         run: nix shell nixpkgs#idris2 -c ./scripts/check-idris2-proofs.sh

.github/workflows/secret-scanner.yml

@@ -23,4 +23,4 @@ jobs:
       pull-requests: write
       actions: read
     uses: hyperpolymath/standards/.github/workflows/secret-scanner-reusable.yml@7fdc2705df74b4e352d2a1cde3e87a5923fdf329
-    secrets: inherit
+    secrets: inherit