Integration: next's file reads go through the checked readers

main's file guard requires reads to pass the automation roots. Loading styles
from a path, the recent-files check and sniffing a dropped file without an
extension read with std::fs directly; they use the engine's io module.

crates/engine/src/cmd/load_styles.rs

@@ -82,7 +82,7 @@ impl Kind {
 fn source(p: &Value, id: &str) -> Result<Document> {
     let (bytes, name) = match (str_param(p, "path"), str_param(p, "base64")) {
         (_, Some(b)) => (super::file::base64_decode(b), str_param(p, "name").unwrap_or("").to_string()),
-        (Some(path), None) => (std::fs::read(path).map_err(|e| bad(id, format!("{path}: {e}")))?, path.to_string()),
+        (Some(path), None) => (crate::io::read_file(path).map_err(|e| bad(id, e))?, path.to_string()),
         _ => return Err(bad(id, "give `path` or `base64`")),
     };
     if name.to_lowercase().ends_with(".idml") {

crates/ui-egui/src/chrome.rs

@@ -1005,7 +1005,7 @@ fn recent_file_stat_at(ctx: &egui::Context, path: &str, now: f64) -> RecentStat
     {
         return st;
     }
-    let meta = std::fs::metadata(path).ok().filter(std::fs::Metadata::is_file);
+    let meta = designcraft_engine::io::metadata(path).ok().filter(designcraft_engine::io::Metadata::is_file);
     let st = RecentStat { exists: meta.is_some(), modified: meta.and_then(|m| m.modified().ok()), checked: now };
     ctx.data_mut(|d| d.insert_temp(key, st.clone()));
     st

crates/ui-egui/src/lib.rs

@@ -1298,7 +1298,7 @@ impl DesignApp {
             return self.run("swatch.load", json!({"path": path}));
         }
         let document = opens_as_document(path)
-            || (std::path::Path::new(path).extension().is_none() && std::fs::read(path).is_ok_and(|b| designcraft_engine::cmd::is_document(&b)));
+            || (std::path::Path::new(path).extension().is_none() && designcraft_engine::io::read(path).is_ok_and(|b| designcraft_engine::cmd::is_document(&b)));
         if document {
             return self.open_file("file.open", json!({"path": path}));
         }