Headless pictures draw on the GPU, with the viewport's pipelines (CPU rasterizer as last tier) (#1555)

Thanks @jyviko.

apps/solidcraft-cli/Cargo.toml

@@ -21,5 +21,10 @@ path = "src/alias.rs"
 
 [dependencies]
 solidcraft-engine = { workspace = true }
+solidcraft-gpu = { workspace = true }
 solidcraft-mcp = { workspace = true }
 serde_json = { workspace = true }
+
+[dev-dependencies]
+# Snapshot tests decode the pictures to compare them with a tolerance.
+image = { workspace = true }