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

.envrc

@@ -14,6 +14,4 @@ if has guix && [ -f guix.scm ] && [ "${USE_GUIX:-0}" = "1" ]; then
   use guix
 fi
 
-if has nix && [ -f flake.nix ] && [ "${USE_FLAKE:-0}" = "1" ]; then
-  use flake
 fi

.github/workflows/hypatia-scan.yml

@@ -24,4 +24,4 @@ permissions:
 jobs:
   hypatia:
     uses: hyperpolymath/standards/.github/workflows/hypatia-scan-reusable.yml@7fdc2705df74b4e352d2a1cde3e87a5923fdf329
-    secrets: inherit
+    secrets: inherit

.github/workflows/proofs.yml

@@ -48,9 +48,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5  # v4
 
-      - name: Install Nix (Determinate installer)
         run: |
-          curl --proto '=https' --tlsv1.2 -sSf -L https://install.determinate.systems/nix \
             | sh -s -- install --no-confirm
 
       - name: Check Idris2 + Lean4 proofs (fail-on-skip, real invocation)
@@ -67,9 +65,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5  # v4
 
-      - name: Install Nix (Determinate installer)
         run: |
-          curl --proto '=https' --tlsv1.2 -sSf -L https://install.determinate.systems/nix \
             | sh -s -- install --no-confirm
 
       - name: Build wasm guests + check ABI signatures vs the verified Idris2 model

.github/workflows/secret-scanner.yml

@@ -16,4 +16,4 @@ jobs:
     permissions:
       contents: read
     uses: hyperpolymath/standards/.github/workflows/secret-scanner-reusable.yml@7fdc2705df74b4e352d2a1cde3e87a5923fdf329
-    secrets: inherit
+    secrets: inherit