feat: agent-base image with ttyd and tmux

Dockerfile and CI for an agent-base container image built on UDI
(Universal Developer Image). Includes ttyd for web terminal access
and pre-built tmux with multi-arch support (x86_64/arm64).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Oleksii Kurinnyi <okurinny@redhat.com>

Author: akurinnoy

.github/workflows/build-image-pr.yml

@@ -0,0 +1,44 @@
+name: Build image (PR validation)
+
+on:
+  pull_request:
+    branches: [main]
+
+env:
+  IMAGE: quay.io/akurinnoy/agent-base
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to Quay.io
+        uses: docker/login-action@v3
+        with:
+          registry: quay.io
+          username: ${{ secrets.QUAY_USERNAME }}
+          password: ${{ secrets.QUAY_PASSWORD }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          platforms: linux/amd64,linux/arm64
+          push: true
+          tags: ${{ env.IMAGE }}:pr-${{ github.event.pull_request.number }}
+
+      - name: Set tag expiration (14 days)
+        run: |
+          EXPIRATION=$(date -u -d '+14 days' +%s)
+          curl -s -X PUT \
+            -u "${{ secrets.QUAY_USERNAME }}:${{ secrets.QUAY_PASSWORD }}" \
+            -H "Content-Type: application/json" \
+            -d "{\"expiration\": ${EXPIRATION}}" \
+            "https://quay.io/api/v1/repository/akurinnoy/agent-base/tag/pr-${{ github.event.pull_request.number }}"

.github/workflows/build-image.yml

@@ -0,0 +1,37 @@
+name: Build and push multi-arch image
+
+on:
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+env:
+  IMAGE: quay.io/akurinnoy/agent-base
+  TAG: latest
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to Quay.io
+        uses: docker/login-action@v3
+        with:
+          registry: quay.io
+          username: ${{ secrets.QUAY_USERNAME }}
+          password: ${{ secrets.QUAY_PASSWORD }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          platforms: linux/amd64,linux/arm64
+          push: true
+          tags: ${{ env.IMAGE }}:${{ env.TAG }}

Dockerfile

@@ -0,0 +1,15 @@
+FROM docker.io/tsl0922/ttyd:1.7.8-alpine AS ttyd
+
+FROM quay.io/devfile/universal-developer-image:ubi9-latest
+
+ARG TARGETARCH
+ARG TMUX_VERSION=3.6a
+
+RUN ARCH=$(case "${TARGETARCH}" in amd64) echo "x86_64" ;; arm64) echo "arm64" ;; *) echo "${TARGETARCH}" ;; esac) && \
+    curl -fsSL "https://github.com/tmux/tmux-builds/releases/download/v${TMUX_VERSION}/tmux-${TMUX_VERSION}-linux-${ARCH}.tar.gz" \
+      | tar xz -C /usr/bin tmux
+
+COPY --from=ttyd /usr/bin/ttyd /usr/bin/ttyd
+
+EXPOSE 7681
+CMD ["/usr/bin/ttyd", "-W", "-p", "7681", "bash"]