Engine: an empty ids names nothing; states.create and conveyor.collect honour id

named_targets reads ids/id as targets() does, so {ids: [], id} can't
pass the gate and then run on nothing.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/engine/src/cmd/library.rs

@@ -117,7 +117,7 @@ pub fn specs() -> Vec<CommandSpec> {
             ok()
         }),
         cmd!(noundo "conveyor.collect", "Collect", [], None, "{ids? (default: the selection)} — each object onto the Content Collector conveyor → {count}", has_selection, |s, p| {
-            let ids = super::ids_param(p, "ids").unwrap_or_else(|| s.active().map(|d| d.selection.items.clone()).unwrap_or_default());
+            let ids = super::targets(s, p)?;
             let keep = s.active().map(|d| d.selection.clone());
             for id in ids {
                 let name = s.doc()?.doc.item(id).map(|it| it.default_label().trim_matches(|c| c == '<' || c == '>').to_string()).unwrap_or_default();

crates/engine/src/cmd/mod.rs

@@ -269,8 +269,9 @@ pub(crate) fn named_targets(spec: &CommandSpec, p: &Value) -> Option<Vec<ItemId>
     if !spec.params.split(|c: char| !c.is_ascii_alphanumeric()).any(|w| w == "ids") {
         return None;
     }
-    if let Some(ids) = ids_param(p, "ids").filter(|v| !v.is_empty()) {
-        return Some(ids);
+    // As `targets` reads them: `ids`, when given, wins over `id` (an empty list names nothing).
+    if let Some(ids) = ids_param(p, "ids") {
+        return (!ids.is_empty()).then_some(ids);
     }
     id_param(p, "id").map(|i| vec![i])
 }

crates/engine/src/cmd/object.rs

@@ -2413,5 +2413,11 @@ mod named_target_tests {
         let e = s.execute("object.textFrameOptions", &json!({"ids": [99999], "columns": 1})).unwrap_err().to_string();
         assert!(e.contains("no object with id 99999"), "{e}");
         assert_eq!(columns(&s), Some(2));
+        // An empty `ids` names nothing (as `targets` reads it), even beside an `id`.
+        let e = s.execute("object.textFrameOptions", &json!({"ids": [], "id": r["id"], "columns": 3})).unwrap_err().to_string();
+        assert!(e.contains("nothing selected"), "{e}");
+        assert_eq!(columns(&s), Some(2));
+        // Commands documented with `ids` honour `id` too.
+        assert_eq!(s.execute("conveyor.collect", &json!({"id": r["id"]})).unwrap()["count"], 1);
     }
 }

crates/engine/src/cmd/states.rs

@@ -3,7 +3,7 @@
 use designcraft_doc::{ItemId, Shape};
 use serde_json::{Value, json};
 
-use super::{CommandSpec, bad, cmd, has_selection, ids_param};
+use super::{CommandSpec, bad, cmd, has_selection};
 use crate::{Result, Session};
 
 fn target(s: &Session, p: &Value) -> Result<ItemId> {
@@ -24,7 +24,7 @@ pub fn specs() -> Vec<CommandSpec> {
             "{ids? (default: the selection; one group's objects or several objects become states)} → {id, states}",
             has_selection,
             |s, p| {
-                let ids = ids_param(p, "ids").unwrap_or_else(|| s.active().map(|d| d.selection.items.clone()).unwrap_or_default());
+                let ids = super::targets(s, p)?;
                 let single_group = ids.len() == 1 && s.doc()?.doc.item(ids[0]).is_some_and(|it| it.shape == Shape::Group && it.children().len() > 1);
                 let gid = if single_group {
                     ids[0]