fix(io/local): resolve symlinks on sandbox root to prevent false escape detection

On macOS, /var is a symlink to /private/var. When New() stores the
unresolved root but validatePath() resolves child paths via EvalSymlinks,
the mismatch causes filepath.Rel to produce ".." prefixes — triggering
false SECURITY sandbox escape warnings on every file operation.

Fix: resolve symlinks on the root path in New() so both sides compare
like-for-like. Updates TestNew to compare against resolved paths.

Co-Authored-By: Virgil <virgil@lethean.io>

pkg/io/local/client.go

@@ -21,6 +21,13 @@ func New(root string) (*Medium, error) {
 	if err != nil {
 		return nil, err
 	}
+	// Resolve symlinks so sandbox checks compare like-for-like.
+	// On macOS, /var is a symlink to /private/var — without this,
+	// EvalSymlinks on child paths resolves to /private/var/... while
+	// root stays /var/..., causing false sandbox escape detections.
+	if resolved, err := filepath.EvalSymlinks(abs); err == nil {
+		abs = resolved
+	}
 	return &Medium{root: abs}, nil
 }
 

pkg/io/local/client_test.go

@@ -12,7 +12,9 @@ func TestNew(t *testing.T) {
 	root := t.TempDir()
 	m, err := New(root)
 	assert.NoError(t, err)
-	assert.Equal(t, root, m.root)
+	// New() resolves symlinks (macOS /var → /private/var), so compare resolved paths.
+	resolved, _ := filepath.EvalSymlinks(root)
+	assert.Equal(t, resolved, m.root)
 }
 
 func TestPath(t *testing.T) {