Add initial nightly build and refactor existing CI workflow

.github/workflows/ci.yml

@@ -0,0 +1,40 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  merge_group:
+
+permissions:
+  contents: read
+
+jobs:
+  checks:
+    name: Checks
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: nightly
+          components: rustfmt
+
+      - name: Run cargo fmt
+        run: cargo +nightly fmt --check
+
+      - uses: dtolnay/rust-toolchain@stable
+      - name: Run cargo clippy
+        run: cargo clippy -- -D warnings
+  test:
+    name: Test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+
+      - name: Get corelib
+        run: git clone https://github.com/starkware-libs/cairo
+      - name: Run cargo test
+        run: CORELIB_PATH="$(pwd)/cairo/corelib/src" cargo test

.github/workflows/nightly.yml

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+name: Nightly
+
+on:
+  schedule:
+    - cron: "0 0 * * *"
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+    name: Build nightly
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+
+      - name: Upgrade Cairo to latest main commit
+        run: cargo xtask upgrade cairo --rev $(git ls-remote --refs "https://github.com/starkware-libs/cairo" main | awk '{print $1}')
+      - name: Get corelib
+        run: git clone https://github.com/starkware-libs/cairo
+      - name: Run cargo test
+        run: CORELIB_PATH="$(pwd)/cairo/corelib/src" cargo test