Move key signatures with Insert Time and Cut Time

Found while testing crates/engine/src/cmd/event.rs:147-196 (insert_time, cut_time); key_signatures in crates/model/src/session.rs:344

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

crates/engine/src/cmd/event.rs

@@ -165,6 +165,11 @@ fn insert_time(e: &mut Engine, p: &Value) -> Result<Value> {
             m.end += r.len();
         }
     }
+    for (at, _) in &mut s.key_signatures {
+        if *at >= r.start {
+            *at = at.saturating_add(r.len());
+        }
+    }
     Ok(json!({"inserted": r.len()}))
 }
 
@@ -192,6 +197,12 @@ fn cut_time(e: &mut Engine, p: &Value) -> Result<Value> {
             m.end -= r.len();
         }
     }
+    s.key_signatures.retain(|(at, _)| !r.contains(*at));
+    for (at, _) in &mut s.key_signatures {
+        if *at >= r.end {
+            *at -= r.len();
+        }
+    }
     Ok(json!({"removed": r.len()}))
 }
 

crates/engine/tests/it/main.rs

@@ -16,5 +16,6 @@ mod random_edits;
 mod recording;
 mod session_transport;
 mod split_into_mono;
+mod time_key_signatures;
 mod track_name_collisions;
 mod trim_to_selection;

crates/engine/tests/it/time_key_signatures.rs

@@ -0,0 +1,41 @@
+use serde_json::json;
+use soundcraft_engine::Engine;
+use soundcraft_model::{ChannelFormat, Session, TrackKind};
+
+fn engine_with_keys() -> Engine {
+    let mut session = Session::default();
+    session.add_track(TrackKind::Audio, ChannelFormat::Mono, None);
+    let mut engine = Engine::new(session);
+    for (at, key) in [(10, "C major"), (48000, "D major"), (100000, "E major")] {
+        engine.execute("event.add_key_change", &json!({"key": key, "at": at})).unwrap();
+    }
+    engine
+}
+
+fn keys(engine: &Engine) -> Vec<(u64, String)> {
+    engine.session().key_signatures.iter().map(|(at, k)| (*at as u64, k.clone())).collect()
+}
+
+fn k(at: u64, key: &str) -> (u64, String) {
+    (at, key.to_string())
+}
+
+#[test]
+fn insert_time_moves_key_signatures() {
+    let mut engine = engine_with_keys();
+    let original = keys(&engine);
+    engine.execute("event.insert_time", &json!({"start": 48000, "length": 1000})).unwrap();
+    assert_eq!(keys(&engine), vec![k(10, "C major"), k(49000, "D major"), k(101000, "E major")]);
+    engine.undo();
+    assert_eq!(keys(&engine), original);
+}
+
+#[test]
+fn cut_time_removes_and_moves_key_signatures() {
+    let mut engine = engine_with_keys();
+    let original = keys(&engine);
+    engine.execute("event.cut_time", &json!({"start": 20, "end": 60000})).unwrap();
+    assert_eq!(keys(&engine), vec![k(10, "C major"), k(40020, "E major")]);
+    engine.undo();
+    assert_eq!(keys(&engine), original);
+}