feat: integrate Nix into CI

.envrc

@@ -0,0 +1 @@
+use flake

.github/actions/run-local-ic-test/action.yml

@@ -6,57 +6,47 @@ inputs:
     required: true
   test-name:
     description: "Name of the test to run"
-    required: true
+  example-name:
+    description: "Name of example to run"
 
 runs:
   using: "composite"
   steps:
-    - name: Cache Build artefacts
-      uses: Swatinem/rust-cache@v2.7.5
+    - name: Restore and cache Nix store
+      uses: nix-community/cache-nix-action@v6
       with:
-        cache-on-failure: true
-        shared-key: ${{ github.event.pull_request.number || github.ref }}
+        # restore and save a cache using this key
+        primary-key: solidity-${{ runner.os }}-${{ hashFiles('Cargo.toml', 'Cargo.lock', 'flake.nix', 'flake.lock') }}
+        # if there's no cache hit, restore a cache by this prefix
+        restore-prefixes-first-match: nix-${{ runner.os }}-
 
-    - name: Get cargo
-      uses: actions-rs/toolchain@v1
-      with:
-        toolchain: stable
+    - uses: nicknovitski/nix-develop@v1
 
-    - name: Download artifacts
-      uses: actions/download-artifact@v4
-      with:
-        name: optimized-contracts
-        path: ./artifacts
+    - name: Pull WASM and Forge artifacts
+      run: |
+        nix build -vL .#valence-cosmwasm-contracts --out-link artifacts
+        nix build -vL .#valence-solidity-contracts --out-link solidity/out
 
-    - name: Download Forge artifacts
-      uses: actions/download-artifact@v4
-      with:
-        name: forge-artifacts
-        path: ./solidity/out/
-
-    - name: List downloaded files
-      shell: bash
+    - name: List artifacts
       run: ls -l ./artifacts
 
-    - name: Download local-ic artifact
-      uses: actions/download-artifact@v4
-      with:
-        name: local-ic
-        path: /tmp
-
-    - name: Make local-ic executable
-      shell: bash
-      run: chmod +x /tmp/local-ic
-
     - name: Start local-ic and wait for it to be ready
       shell: bash
       run: ./scripts/start-local-ic.sh ${{ inputs.chain-config }}
 
+    - name: Run local-ic example
+      if: ${{ inputs.example-name != '' }}
+      shell: bash
+      env:
+        RUST_LOG: debug
+      run: nix shell .#valence-program-examples --command ${{ inputs.test-name }}
+
     - name: Run local-ic test
+      if: ${{ inputs.test-name != '' }}
       shell: bash
       env:
         RUST_LOG: debug
-      run: cargo run --package valence-e2e --example ${{ inputs.test-name }}
+      run: nix shell .#valence-e2e --command ${{ inputs.example-name }}
 
     - name: Cleanup
       shell: bash