ui: a new document clears the viewport's picks; opening a sample says so

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo

crates/ui-egui/src/lib.rs

@@ -1404,6 +1404,11 @@ impl ModelApp {
                 self.selected = None;
                 self.selected_seed = None;
                 self.reply = None;
+                // Picks are by name, and the names of another document are other things.
+                if !self.pick.selection.is_empty() {
+                    self.pick.selection.clear();
+                    self.pick.generation = self.pick.generation.wrapping_add(1);
+                }
             }
             self.framed_document = Some(self.session.opened());
             self.reframe = framing::Reframe::merge(self.reframe, framing::Reframe::Home);
@@ -1748,6 +1753,7 @@ mod tests {
         app.run("file.sample", json!({"name": "cantilever"})).unwrap();
         assert_eq!(app.model_name(), "Cantilever (sample)");
         let status = |app: &ModelApp| app.status.as_ref().map(|s| s.text.clone()).unwrap_or_default();
+        assert_eq!(status(&app), "Opened the Cantilever sample");
         app.run("solve.run", json!({})).unwrap();
         assert_eq!(status(&app), "Solved 2 steps");
         app.run("results.deformed", json!({"step": "Load", "show": true})).unwrap();

crates/ui-egui/src/reply.rs

@@ -112,6 +112,10 @@ pub fn done(command: &str, label: &str, params: &Value, v: &Value) -> String {
             None => format!("Showing {step}, last frame"),
         }),
         "results.clear" => Some("Back to the model".to_string()),
+        "file.sample" => {
+            let label = v.get("sample").and_then(Value::as_str).and_then(fieldcraft_engine::sample::find).map(|s| s.label);
+            label.map(|l| format!("Opened the {l} sample"))
+        }
         "solve.run" => v.get("steps").and_then(Value::as_array).map(|s| format!("Solved {}", plural(s.len() as u64, "step"))),
         c if c.starts_with("solve.") => Some(format!("Solved {step}", step = params["step"].as_str().unwrap_or("the step"))),
         _ => None,