feat(ucs): interactive UCS command — UCS Z 90 typable everywhere (F2, #169)

Bare `UCS` now enters an interactive front-end (UcsCommand) that gathers the
option then its value as separate steps, instead of the command line
submitting `UCS` alone on the first Space. The front-end delegates execution
back to the existing inline `UCS <option> …` handler via a new
`CmdResult::Dispatch(String)`, so the coordinate-system math and the
save/persist path are untouched.

Now `UCS Z 90` works the same from the command line (Space-separated),
headless automation, and any source that feeds the active command — closing
the input half of #169. Inline `UCS Z 90` (one-shot / paste) still hits the
inline handler directly.

Second phase of routing input sources through the unified step driver: the
interactive command is driven by feed_command like any tool. Adds headless
test ucs_interactive_inline_args.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/app/automation.rs

@@ -565,6 +565,27 @@ mod tests {
         assert_eq!(app.automation_op(r#"{"op":"run"}"#)["ok"], false);
     }
 
+    #[test]
+    fn ucs_interactive_inline_args() {
+        // `UCS Z 90` must drive the interactive UCS command step-by-step (option
+        // "Z" then value "90") and rotate the active UCS 90° about Z. (#169)
+        let mut app = OpenCADStudio::new_for_test();
+        app.automation_op(r#"{"op":"new"}"#);
+        app.automation_op(r#"{"op":"run","cmd":"UCS Z 90"}"#);
+        let i = app.active_tab;
+        let ucs = app.tabs[i]
+            .active_ucs
+            .as_ref()
+            .expect("UCS Z 90 should set an active UCS");
+        // 90° about Z sends the X axis (1,0,0) → (0,1,0).
+        assert!(
+            ucs.x_axis.x.abs() < 1e-6 && (ucs.x_axis.y - 1.0).abs() < 1e-6,
+            "x_axis after UCS Z 90 = ({}, {})",
+            ucs.x_axis.x,
+            ucs.x_axis.y
+        );
+    }
+
     #[test]
     fn save_then_open_round_trips() {
         let mut app = OpenCADStudio::new_for_test();

src/app/cmd_result.rs

@@ -567,6 +567,15 @@ impl OpenCADStudio {
                 self.restore_pre_cmd_tangent();
                 let _ = self.dispatch_command(&cmd);
             }
+            CmdResult::Dispatch(cmd) => {
+                // End this interactive front-end, then run the assembled command
+                // through the normal dispatcher. Selection is left untouched.
+                self.tabs[i].active_cmd = None;
+                self.tabs[i].snap_result = None;
+                self.tabs[i].scene.clear_preview_wire();
+                self.restore_pre_cmd_tangent();
+                let _ = self.dispatch_command(&cmd);
+            }
             CmdResult::MatchEntityLayer { dest, src } => {
                 self.tabs[i].active_cmd = None;
                 self.tabs[i].snap_result = None;

src/app/commands.rs

@@ -3618,8 +3618,18 @@ impl OpenCADStudio {
                 }
             }
 
-            // ── UCS management ───────────────────────────────────────────
-            cmd if cmd == "UCS" || cmd.starts_with("UCS ") => {
+            // Bare UCS → interactive front-end (option then value as steps), so
+            // `UCS Z 90` is typable in the command line and works headlessly.
+            // The front-end delegates back to the inline handler below. (#169)
+            "UCS" => {
+                use crate::modules::view::ucs_cmd::UcsCommand;
+                let cmd_obj = UcsCommand::new();
+                self.command_line.push_info(&cmd_obj.prompt());
+                self.tabs[i].active_cmd = Some(Box::new(cmd_obj));
+            }
+
+            // ── UCS management (inline `UCS <option> …`) ─────────────────────
+            cmd if cmd.starts_with("UCS ") => {
                 use super::helpers::{ucs_rotated_z, ucs_to_wcs, ucs_z_axis};
                 use acadrust::tables::Ucs;
                 use acadrust::types::Vector3;