geometry: read tagged meshes through the VFS, refuse singular transforms, share the model's coordinate limit (#6)

read_3mf_file reads through solidcraft_io::vfs like open_design_file (regular files only,
browser files too), so the engine drops its own capped reader and EngineError::File.
A build item whose transform flattens its object is an error, and coordinates use
modelcraft_model::MAX_COORD (1e9) instead of a looser limit of their own.


Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

Co-authored-by: jyviko <2501648+jyviko@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/engine/src/cmd/geometry.rs

@@ -1,10 +1,9 @@
 use std::sync::Arc;
 
-use modelcraft_geometry::tagged_mesh::{self, MAX_FILE_BYTES};
+use modelcraft_geometry::tagged_mesh;
 use modelcraft_geometry::{Shape, open_design_file};
 use serde_json::{Value, json};
 
-use super::read_capped;
 use crate::{CommandSpec, EngineError, Result, Session};
 
 pub const OPEN: CommandSpec = CommandSpec {
@@ -93,7 +92,7 @@ fn import_mesh(s: &mut Session, p: &Value) -> Result<Value> {
         .and_then(Value::as_str)
         .filter(|x| !x.trim().is_empty() && x.len() < 4096)
         .ok_or_else(|| EngineError::Params("`path` must name a .3mf file".into()))?;
-    let surfaces = tagged_mesh::read_3mf(&read_capped(path, MAX_FILE_BYTES)?)?;
+    let surfaces = tagged_mesh::read_3mf_file(path)?;
     let first = s.surfaces.len();
     let added: Vec<Value> = surfaces
         .iter()
@@ -139,7 +138,15 @@ mod tests {
         assert_eq!(s.surfaces[0].mesh.tri_face, vec![0, 1, 1, 1]);
         assert_eq!(s.journal.len(), 1);
 
-        for p in [json!({"path": junk.to_str().unwrap()}), json!({"path": dir.join("missing.3mf").to_str().unwrap()}), json!({"path": ""})] {
+        let hostile = [
+            json!({"path": junk.to_str().unwrap()}),
+            json!({"path": dir.join("missing.3mf").to_str().unwrap()}),
+            json!({"path": dir.to_str().unwrap()}),
+            json!({"path": "/dev/zero"}),
+            json!({"path": ""}),
+            json!({"path": "x".repeat(5000)}),
+        ];
+        for p in hostile {
             assert!(s.execute("geometry.import.mesh", &p).is_err(), "{p}");
         }
         assert_eq!(s.surfaces.len(), 1);

crates/engine/src/cmd/mod.rs

@@ -38,17 +38,3 @@ pub(crate) fn xyz(p: &Value, key: &str) -> Result<[f64; 3]> {
     }
     Ok(out)
 }
-
-/// A file's bytes, refusing anything over `cap`.
-pub(crate) fn read_capped(path: &str, cap: usize) -> Result<Vec<u8>> {
-    use std::io::Read;
-    let err = |e: std::io::Error| EngineError::File(format!("{path}: {e}"));
-    let f = std::fs::File::open(path).map_err(err)?;
-    let len = f.metadata().map(|m| m.len()).unwrap_or(0);
-    let mut bytes = Vec::with_capacity(usize::try_from(len).unwrap_or(0).min(cap));
-    f.take(cap as u64 + 1).read_to_end(&mut bytes).map_err(err)?;
-    if bytes.len() > cap {
-        return Err(EngineError::File(format!("{path}: larger than {} MB", cap >> 20)));
-    }
-    Ok(bytes)
-}