ci: split workflows for linear development flow

Reshapes .gitea/workflows/ around the new main ← development ←
feature/* branching model:

- go-unit.yaml — Go unit tests, runs on push/PR matching Go paths
- ui-test.yaml — narrowed to Vitest + Playwright only (Go tests now
  live in go-unit.yaml)
- integration.yaml — testcontainers suite, fires on PR to
  development/main and on push to development
- dev-deploy.yaml — builds the stack and (re)deploys tools/dev-deploy/
  on every merge into development
- prod-build.yaml — builds prod images on push to main and uploads
  docker save bundles as artifacts (30-day retention)
- deploy-prod.yaml — workflow_dispatch placeholder for the future
  SSH-based rollout

ui-release.yaml is removed; its v* tag trigger is superseded by
prod-build.yaml plus the manual deploy-prod entry point.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitea/workflows/prod-build.yaml

@@ -0,0 +1,116 @@
+name: prod-build
+
+# Builds the production-grade Docker images and the UI bundle on every
+# merge into `main`, then saves the artifacts so a future
+# `deploy-prod.yaml` run can ship them to the production host. This
+# workflow does not deploy anything by itself — production rollout is
+# strictly manual (workflow_dispatch on `deploy-prod.yaml`).
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - 'backend/**'
+      - 'gateway/**'
+      - 'game/**'
+      - 'pkg/**'
+      - 'ui/**'
+      - 'go.work'
+      - 'go.work.sum'
+      - '.gitea/workflows/prod-build.yaml'
+      - '!**/*.md'
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        shell: bash
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          submodules: recursive
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version-file: go.work
+          cache: true
+
+      - name: Set up pnpm
+        uses: pnpm/action-setup@v4
+        with:
+          version: 11.0.7
+
+      - name: Set up Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: pnpm
+          cache-dependency-path: ui/pnpm-lock.yaml
+
+      - name: Resolve image tag
+        id: tag
+        run: |
+          short_sha=$(git rev-parse --short=12 HEAD)
+          echo "tag=commit-${short_sha}" >>"$GITHUB_OUTPUT"
+
+      - name: Build backend image
+        run: |
+          docker build \
+            -t "galaxy/backend:${{ steps.tag.outputs.tag }}" \
+            -f backend/Dockerfile \
+            .
+
+      - name: Build gateway image
+        run: |
+          docker build \
+            -t "galaxy/gateway:${{ steps.tag.outputs.tag }}" \
+            -f gateway/Dockerfile \
+            .
+
+      - name: Build engine image
+        run: |
+          docker build \
+            -t "galaxy/game-engine:${{ steps.tag.outputs.tag }}" \
+            -f game/Dockerfile \
+            .
+
+      - name: Install UI dependencies
+        working-directory: ui
+        run: pnpm install --frozen-lockfile
+
+      - name: Build UI bundle
+        working-directory: ui/frontend
+        env:
+          VITE_GATEWAY_BASE_URL: https://api.galaxy.com
+        run: |
+          # Production response-signing public key is not in the repo
+          # yet (the dev key in `tools/local-dev/keys/` is for dev
+          # only). When real prod keys exist, source them from a Gitea
+          # Actions secret and set VITE_GATEWAY_RESPONSE_PUBLIC_KEY
+          # here. Until then the prod bundle compiles with the dev
+          # key as a placeholder so the artifact exists.
+          export VITE_GATEWAY_RESPONSE_PUBLIC_KEY="$(grep -E '^VITE_GATEWAY_RESPONSE_PUBLIC_KEY=' .env.development | cut -d= -f2)"
+          pnpm build
+
+      - name: Save images as artifact bundles
+        run: |
+          mkdir -p artifacts
+          docker save "galaxy/backend:${{ steps.tag.outputs.tag }}" \
+            | gzip >"artifacts/backend-${{ steps.tag.outputs.tag }}.tar.gz"
+          docker save "galaxy/gateway:${{ steps.tag.outputs.tag }}" \
+            | gzip >"artifacts/gateway-${{ steps.tag.outputs.tag }}.tar.gz"
+          docker save "galaxy/game-engine:${{ steps.tag.outputs.tag }}" \
+            | gzip >"artifacts/game-engine-${{ steps.tag.outputs.tag }}.tar.gz"
+          tar -C ui/frontend -czf \
+            "artifacts/ui-dist-${{ steps.tag.outputs.tag }}.tar.gz" build
+
+      - name: Upload images
+        uses: actions/upload-artifact@v4
+        with:
+          name: galaxy-images-${{ steps.tag.outputs.tag }}
+          path: artifacts/*.tar.gz
+          retention-days: 30