Include outline when predicting edits with Zeta (#22895)

Release Notes:

- N/A

Co-authored-by: Thorsten <thorsten@zed.dev>

crates/rpc/src/llm.rs

@@ -36,6 +36,7 @@ pub struct PerformCompletionParams {
 
 #[derive(Debug, Serialize, Deserialize)]
 pub struct PredictEditsParams {
+    pub outline: Option<String>,
     pub input_events: String,
     pub input_excerpt: String,
 }