Vendor opencode source for docker build

opencode/.github/actions/setup-bun/action.yml

@@ -0,0 +1,19 @@
+name: "Setup Bun"
+description: "Setup Bun with caching and install dependencies"
+runs:
+  using: "composite"
+  steps:
+    - name: Mount Bun Cache
+      uses: useblacksmith/stickydisk@v1
+      with:
+        key: ${{ github.repository }}-bun-cache-${{ runner.os }}
+        path: ~/.bun
+
+    - name: Setup Bun
+      uses: oven-sh/setup-bun@v2
+      with:
+        bun-version-file: package.json
+
+    - name: Install dependencies
+      run: bun install
+      shell: bash