ci: add scheduled property-test workflow

.github/workflows/ci.yaml

@@ -99,7 +99,7 @@ jobs:
         run: nix develop --command bash -c "mix deps.get"
 
       - name: Unit Tests
-        run: nix develop --command bash -c "mix test"
+        run: nix develop --command bash -c "mix test --exclude property"
 
   lint:
     runs-on: ubuntu-latest
@@ -163,4 +163,3 @@ jobs:
 
       - name: Run dialyzer
         run: nix develop --command bash -c 'mix dialyzer --format github'
-

.github/workflows/proptest.yaml

@@ -0,0 +1,74 @@
+name: Property Tests
+on:
+  schedule:
+    - cron: "0 0 * * *"
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  issues: write
+
+concurrency:
+  group: proptest
+  cancel-in-progress: false
+
+jobs:
+  proptest:
+    runs-on: ubuntu-latest
+    env:
+      SPITFIRE_PROPERTY_MAX_RUNS: "250000"
+
+    steps:
+      - uses: actions/checkout@v4
+      - uses: DeterminateSystems/nix-installer-action@main
+      - uses: cachix/cachix-action@v14
+        with:
+          name: elixir-tools
+          authToken: "${{ secrets.CACHIX_AUTH_TOKEN }}"
+
+      - uses: actions/cache@v4
+        with:
+          path: |
+            deps
+            _build
+          key: ${{ runner.os }}-mix-${{ hashFiles('**/.mise.toml') }}-${{ hashFiles('**/mix.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-mix-${{ hashFiles('**/.mise.toml') }}-
+
+      - name: Install Dependencies
+        run: nix develop --command bash -c "mix deps.get"
+
+      - name: Run property tests
+        shell: bash
+        run: |
+          set -euo pipefail
+
+          nix develop --command bash -c "mix test --only property" 2>&1 | tee property-test.log
+
+      - name: Build failure report
+        if: ${{ failure() }}
+        shell: bash
+        run: |
+          {
+            echo "## Property tests failed"
+            echo ""
+            echo "- Workflow run: ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}"
+            echo "- Branch: \`${{ github.ref_name }}\`"
+            echo "- Commit: \`${{ github.sha }}\`"
+            echo "- Trigger: \`${{ github.event_name }}\`"
+            echo ""
+            echo "### Log tail"
+            echo '```text'
+            tail -n 400 property-test.log || true
+            echo '```'
+          } > property-test-failure.md
+
+      - name: Open issue on failure
+        if: ${{ failure() }}
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          gh issue create \
+            --repo "${{ github.repository }}" \
+            --title "Property tests failed (run #${{ github.run_number }})" \
+            --body-file property-test-failure.md