Embed the game data so the disks are not needed at run time

build.rs unpacks the ADF images next to Cargo.toml (or in
SKIDS_EMBED_DIR) with the same ADF/LHA readers the game uses and packs
the files into the executable. At run time the built-in data loads
first and anything given with --data, or found next to the executable,
overrides it. The embed feature is on by default; builds without it
behave as before and ask for --data. CI now runs the binary from an
empty directory.

.github/workflows/build.yml

@@ -31,11 +31,14 @@ jobs:
         run: cargo test --release
       - name: Build
         run: cargo build --release
-      - name: Check against the game data
+      - name: Check the binary runs without the disks
         shell: bash
         run: |
-          ./target/release/${{ matrix.bin }} info --data .
-          ./target/release/${{ matrix.bin }} bench --data . --seconds 60
+          mkdir -p "$RUNNER_TEMP/standalone"
+          cp target/release/${{ matrix.bin }} "$RUNNER_TEMP/standalone/"
+          cd "$RUNNER_TEMP/standalone"
+          ./${{ matrix.bin }} info
+          ./${{ matrix.bin }} bench --seconds 60
       - uses: actions/upload-artifact@v4
         with:
           name: ${{ matrix.artifact }}