ci: opt into Node.js 24 and fix checkout in opencode workflow

.github/workflows/ci.yml

@@ -10,6 +10,7 @@ on:
 
 env:
   CARGO_TERM_COLOR: always
+  FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: "true"
 
 jobs:
   # Test job

.github/workflows/opencode.yml

@@ -0,0 +1,34 @@
+name: opencode
+on:
+  issue_comment:
+    types: [created]
+  pull_request_review_comment:
+    types: [created]
+
+env:
+  FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: "true"
+
+jobs:
+  opencode:
+    if: |
+      contains(github.event.comment.body, '/oc') ||
+      contains(github.event.comment.body, '/opencode')
+    runs-on: ubuntu-latest
+    permissions:
+      id-token: write
+      contents: write
+      pull-requests: write
+      issues: write
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 1
+
+      - name: Run OpenCode
+        uses: anomalyco/opencode/github@latest
+        env:
+          ANTHROPIC_API_KEY: ${{ secrets.ANTHROPIC_API_KEY }}
+        with:
+          model: anthropic/claude-sonnet-4-20250514