ci: add Slither static-analysis

.github/workflows/contracts.yml

@@ -136,4 +136,57 @@
         run: npx hardhat compile
 
       - name: Run hardhat tests
-        run: npx hardhat test
+        run: npx hardhat test
+
+  lint:
+    if: github.event.pull_request.draft == false
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '18'
+      - run: yarn install --frozen-lockfile
+
+      - uses: foundry-rs/foundry-toolchain@v1   # stable channel is fine
+      - name: Check Solidity formatting
+        run: forge fmt --check
+
+      - name: Check JS/docs formatting
+        run: npx prettier --check "**/*.{js,ts,jsx,tsx,md,json,yml,yaml}"
+
+  slither:
+    needs: foundry                              
+    runs-on: ubuntu-latest
+    env:
+      FOUND_OUT_DIR: artifacts                  
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with: { node-version: '18' }
+      - run: yarn install --frozen-lockfile
+
+      - uses: foundry-rs/foundry-toolchain@v1
+        with: { version: nightly }              
+      - run: forge build --build-info --evm-version cancun
+
+      - uses: actions/setup-python@v5
+        with: { python-version: '3.11' }
+      - run: |
+          python -m pip install --upgrade pip
+          pip install slither-analyzer==0.11.0
+      - name: Run Slither
+        run: |
+          slither . \
+            --foundry-out-directory "$FOUND_OUT_DIR" \
+            --exclude-dependencies \
+            --json slither-report.json \
+            --markdown-root slither-report.md
+      - uses: actions/upload-artifact@v4
+        with:
+          name: slither-static-analysis
+          path: |
+            slither-report.json
+            slither-report.md