ci: add opencode integration

Author: observerw

.github/workflows/opencode.yml

@@ -0,0 +1,32 @@
+name: opencode
+
+on:
+  issue_comment:
+    types: [created]
+  pull_request_review_comment:
+    types: [created]
+
+jobs:
+  opencode:
+    if: |
+      contains(github.event.comment.body, ' /oc') ||
+      startsWith(github.event.comment.body, '/oc') ||
+      contains(github.event.comment.body, ' /opencode') ||
+      startsWith(github.event.comment.body, '/opencode')
+    runs-on: ubuntu-latest
+    permissions:
+      id-token: write
+      contents: read
+      pull-requests: read
+      issues: read
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Run opencode
+        uses: sst/opencode/github@latest
+        env:
+          GOOGLE_GENERATIVE_AI_API_KEY: ${{ secrets.GOOGLE_GENERATIVE_AI_API_KEY }}
+          GEMINI_API_KEY: ${{ secrets.GEMINI_API_KEY }}
+        with:
+          model: google/gemini-3-flash-preview