Add Forgejo Actions workflow to build and deploy on push

- .forgejo/workflows/deploy.yaml: build the wasm bundle on the arch-latest
  Docker runner and rsync it into the bind-mounted web root (/deploy) on
  push to master
- deploy/Caddyfile.example: reference site block with the cross-origin
  isolation headers the WASM runtime requires

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.forgejo/workflows/deploy.yaml

@@ -0,0 +1,96 @@
+name: Deploy
+
+on:
+  push:
+    branches: [master]
+  workflow_dispatch:
+
+# One deploy at a time; if you push twice quickly, cancel the older run so the
+# newest commit is what lands on the server.
+concurrency:
+  group: deploy
+  cancel-in-progress: true
+
+jobs:
+  build-deploy:
+    runs-on: arch-latest
+    steps:
+      - name: Install build dependencies
+        run: |
+          # Same keyring bootstrap the Crafter.Build CI does: the slim
+          # archlinux:latest image ships without a populated pacman keyring
+          # or local master key.
+          pacman-key --init
+          pacman-key --populate archlinux
+          pacman -Sy --noconfirm --needed archlinux-keyring
+          pacman -Syu --noconfirm --needed \
+            clang lld libc++ \
+            wasi-libc wasi-libc++ wasi-libc++abi wasi-compiler-rt \
+            git curl tar rsync
+          # Container runs as root; workspace may be owned by another uid.
+          git config --global --add safe.directory '*'
+
+      - name: Install crafter-build
+        # Pull the rolling 'latest' Linux build from the Crafter.Build repo and
+        # install it distro-style so it auto-discovers its modules under
+        # /usr/share/crafter-build. v2 = SSE4.2 baseline, safe on the CI SBC.
+        run: |
+          set -eux
+          url="https://forgejo.catcrafts.net/Catcrafts/Crafter.Build/releases/download/latest/crafter-build-linux-x86_64-v2.tar.gz"
+          mkdir -p /tmp/cb
+          curl -fsSL "$url" -o /tmp/cb.tar.gz
+          tar -xzf /tmp/cb.tar.gz -C /tmp/cb
+          install -Dm755 /tmp/cb/bin/crafter-build /usr/bin/crafter-build
+          cp -r /tmp/cb/share/crafter-build /usr/share/
+          crafter-build --version || true
+
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Cache crafter-build dependency clones
+        # ~/.cache/crafter.build holds the Crafter.Graphics clone and prebuilt
+        # module cache. crafter-build still git-pulls the dep each run, so a
+        # stale cache only means a smaller delta fetch, never a stale build.
+        uses: actions/cache@v4
+        with:
+          path: ~/.cache/crafter.build
+          key: crafter-cache-${{ runner.os }}-${{ hashFiles('project.cpp') }}
+          restore-keys: |
+            crafter-cache-${{ runner.os }}-
+
+      - name: Build (wasm bundle)
+        run: crafter-build
+
+      - name: Locate build output
+        id: out
+        run: |
+          set -eu
+          dist=$(find bin -maxdepth 1 -type d -name 'Catcrafts.Net-wasm32-wasip1-*' | head -n1)
+          if [ -z "$dist" ]; then
+            echo "No build output directory found under bin/" >&2
+            ls -la bin || true
+            exit 1
+          fi
+          echo "dist=$dist" >> "$GITHUB_OUTPUT"
+          echo "Built bundle: $dist"
+          ls -la "$dist"
+
+      - name: Deploy to web root
+        # No SSH: the job already runs on the deploy box. The server's web root
+        # is bind-mounted into this container at /deploy via the runner config
+        # (container.options: "-v /path/to/webroot:/deploy"). We just copy into
+        # it. --delete makes the root an exact mirror of the build; Caddyfile.coi
+        # is a local dev helper (its 'root' points at the build machine), so the
+        # server's own Caddy config supplies the headers instead.
+        env:
+          DIST: ${{ steps.out.outputs.dist }}
+        run: |
+          set -eu
+          if [ ! -d /deploy ]; then
+            echo "ERROR: /deploy is not mounted into the runner container." >&2
+            echo "Add '-v /your/webroot:/deploy' to the runner's container.options" >&2
+            echo "in config.yaml and restart the runner." >&2
+            exit 1
+          fi
+          rsync -a --delete --exclude 'Caddyfile.coi' "$DIST"/ /deploy/
+          echo "Deployed $DIST -> /deploy (host web root)"