Implement pure Rust visual snapshots (#132)

crates/metacrate-grid-agent/tests/dependency_policy.rs

@@ -2,10 +2,14 @@ use std::collections::BTreeSet;
 use std::fs;
 use std::path::{Path, PathBuf};
 
-const ALLOWED_DEPENDENCIES: [&str; 13] = [
+const ALLOWED_DEPENDENCIES: [&str; 17] = [
+    "base64",
     "crossterm",
     "libremetaverse",
+    "libremetaverse-imaging",
+    "libremetaverse-rendering-simple",
     "metacrate-lsl-tools",
+    "png",
     "libremetaverse-types",
     "reqwest",
     "rustls",
@@ -48,10 +52,10 @@ fn package_has_only_reviewed_rust_dependencies_and_no_build_script() {
 #[test]
 fn runtime_source_has_no_subprocess_or_native_abi_escape_hatch() {
     let source = PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("src");
-    let mut files = Vec::with_capacity(34);
+    let mut files = Vec::with_capacity(36);
     collect_rust_files(&source, &mut files);
     assert!(
-        files.len() <= 34,
+        files.len() <= 36,
         "source-file count needs a reviewed bound update"
     );
     for path in files {
@@ -82,6 +86,27 @@ fn runtime_source_has_no_subprocess_or_native_abi_escape_hatch() {
     }
 }
 
+#[test]
+fn vision_path_selects_only_the_pure_rust_renderer_and_codec() {
+    let root = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
+    let manifest = fs::read_to_string(root.join("Cargo.toml")).expect("agent manifest");
+    assert!(manifest.contains("default-features = false, features = [\"rust-j2k\"]"));
+    for forbidden in ["imaging-skia", "openjpeg", "skia-safe"] {
+        assert!(!manifest.contains(forbidden), "vision enables {forbidden}");
+    }
+    let renderer = fs::read_to_string(root.join("../libremetaverse-rendering-simple/Cargo.toml"))
+        .expect("simple renderer manifest");
+    assert!(!renderer.contains("imaging-skia"));
+    assert!(!renderer.contains("openjpeg"));
+    let vision = fs::read_to_string(root.join("src/vision.rs")).expect("vision source");
+    for forbidden in ["screenshot crate", "gpu adapter", "std::process"] {
+        assert!(
+            !vision.to_ascii_lowercase().contains(forbidden),
+            "vision must remain synthetic and pure Rust: {forbidden}"
+        );
+    }
+}
+
 #[test]
 fn compatibility_crates_never_depend_on_or_reexport_metacrate_crates() {
     let workspace = PathBuf::from(env!("CARGO_MANIFEST_DIR"))