Part of #785: run and command_batch steps can use earlier results

A run (vectorcraft-cli run, the MCP command_batch tool) had no way to use
an id an earlier step returned. A parameter string that is exactly
$N.path or $last.path now takes that value from step N's result
(0-based), e.g. {"id":"$1.id"}; $$ starts a literal $, and a
reference to nothing fails the step. Objects given to a command are now
used as given: an ids element or id that isn't an object id (or an
unresolved reference) fails instead of the command acting on the
selection. text.setRangeStyle styles the selected type object when no
id is given, as text.setStyle does.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

apps/vectorcraft-cli/src/main.rs

@@ -269,17 +269,23 @@ fn run(args: &[String]) -> Result<(), String> {
     } else if !matches!(steps.first(), Some(Step::Cmd(id, _)) if id == "file.new") {
         h.ensure_document();
     }
+    // Each step's result, for later steps to refer to (`"$1.id"`, see `vectorcraft_engine::steps`).
+    let mut results = vec![];
     for step in steps {
-        match step {
+        let r = match step {
             Step::Cmd(id, params) => {
+                let params = vectorcraft_engine::steps::resolve(&params, &results).map_err(|e| format!("{id}: {e}"))?;
                 let r = h.call("engine.execute", json!({"command": id, "params": params})).map_err(|e| format!("{id}: {e}"))?;
                 emit(json!({"step": "cmd", "command": id, "result": r}))?;
+                r
             }
             Step::Export(path) => {
                 let r = h.call("app.export", json!({"path": path, "scale": scale})).map_err(|e| format!("export {path}: {e}"))?;
                 emit(json!({"step": "export", "result": r}))?;
+                r
             }
-        }
+        };
+        results.push(r);
     }
     Ok(())
 }