feat(git): add latest buildable update workflow

.github/workflows/update-latest-buildable.yml

@@ -0,0 +1,70 @@
+name: Update latest buildable
+
+on:
+  workflow_dispatch:
+    inputs:
+      ref:
+        description: "Buildable ref, for example buildable/v0.5.0"
+        required: true
+        type: string
+  push:
+    tags:
+      - "buildable/*"
+
+permissions:
+  contents: write
+
+jobs:
+  update-latest-buildable:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Resolve buildable ref
+        id: buildable
+        run: |
+          if [ "${{ github.event_name }}" = "workflow_dispatch" ]; then
+            echo "ref=${{ inputs.ref }}" >> "$GITHUB_OUTPUT"
+          else
+            echo "ref=${GITHUB_REF_NAME}" >> "$GITHUB_OUTPUT"
+          fi
+
+      - name: Checkout master
+        uses: actions/checkout@v4
+        with:
+          ref: master
+
+      - name: Update latestBuildable
+        run: |
+          python3 - <<'PY'
+          import json
+          from pathlib import Path
+
+          ref = "${{ steps.buildable.outputs.ref }}"
+          index_path = Path("registry/index.json")
+
+          index = json.loads(index_path.read_text(encoding="utf-8"))
+
+          index["partner"]["latestBuildable"] = {
+              "url": "https://github.com/slhaf/Partner.git",
+              "ref": ref
+          }
+
+          index_path.write_text(
+              json.dumps(index, ensure_ascii=False, indent=2) + "\n",
+              encoding="utf-8"
+          )
+          PY
+
+      - name: Commit registry update
+        run: |
+          if git diff --quiet registry/index.json; then
+            echo "No latestBuildable changes."
+            exit 0
+          fi
+
+          git config user.name "github-actions[bot]"
+          git config user.email "github-actions[bot]@users.noreply.github.com"
+
+          git add registry/index.json
+          git commit -m "chore(registry): update latest buildable to ${{ steps.buildable.outputs.ref }}"
+          git push