ep: Send trigger in header (#56433)

Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Closes #ISSUE

Release Notes:

- N/A or Added/Fixed/Improved ...

crates/cloud_llm_client/src/cloud_llm_client.rs

@@ -115,7 +115,9 @@ pub struct PredictEditsBody {
     pub trigger: PredictEditsRequestTrigger,
 }
 
-#[derive(Default, Debug, Clone, Copy, Serialize, Deserialize, strum::AsRefStr)]
+#[derive(
+    Default, Debug, Clone, Copy, Serialize, Deserialize, strum::AsRefStr, strum::EnumString,
+)]
 #[strum(serialize_all = "snake_case")]
 pub enum PredictEditsRequestTrigger {
     Testing,

crates/cloud_llm_client/src/predict_edits_v3.rs

@@ -1,4 +1,3 @@
-use crate::PredictEditsRequestTrigger;
 use serde::{Deserialize, Serialize};
 use std::borrow::Cow;
 use std::ops::Range;
@@ -6,6 +5,7 @@ use strum::{AsRefStr, EnumString};
 
 pub const PREDICT_EDITS_MODE_HEADER_NAME: &str = "X-Zed-Predict-Edits-Mode";
 pub const PREDICT_EDITS_REQUEST_ID_HEADER_NAME: &str = "X-Zed-Predict-Edits-Request-Id";
+pub const PREDICT_EDITS_TRIGGER_HEADER_NAME: &str = "X-Zed-Predict-Edits-Trigger";
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize, AsRefStr, EnumString)]
 #[serde(rename_all = "snake_case")]
@@ -32,8 +32,6 @@ pub struct RawCompletionRequest {
 pub struct PredictEditsV3Request {
     #[serde(flatten)]
     pub input: zeta_prompt::ZetaPromptInput,
-    #[serde(default)]
-    pub trigger: PredictEditsRequestTrigger,
 }
 
 #[derive(Debug, Deserialize, Serialize)]

crates/edit_prediction/src/edit_prediction.rs

@@ -3,8 +3,9 @@ use client::{Client, EditPredictionUsage, NeedsLlmTokenRefresh, UserStore, globa
 use cloud_api_client::LlmApiToken;
 use cloud_api_types::{OrganizationId, SubmitEditPredictionFeedbackBody};
 use cloud_llm_client::predict_edits_v3::{
-    PREDICT_EDITS_MODE_HEADER_NAME, PREDICT_EDITS_REQUEST_ID_HEADER_NAME, PredictEditsMode,
-    PredictEditsV3Request, PredictEditsV3Response, RawCompletionRequest, RawCompletionResponse,
+    PREDICT_EDITS_MODE_HEADER_NAME, PREDICT_EDITS_REQUEST_ID_HEADER_NAME,
+    PREDICT_EDITS_TRIGGER_HEADER_NAME, PredictEditsMode, PredictEditsV3Request,
+    PredictEditsV3Response, RawCompletionRequest, RawCompletionResponse,
 };
 use cloud_llm_client::{
     EditPredictionRejectReason, EditPredictionRejection,
@@ -2600,7 +2601,7 @@ impl EditPredictionStore {
             .http_client()
             .build_zed_llm_url("/predict_edits/v3", &[])?;
 
-        let request = PredictEditsV3Request { input, trigger };
+        let request = PredictEditsV3Request { input };
         let request_id = uuid::Uuid::new_v4().to_string();
 
         let json_bytes = serde_json::to_vec(&request)?;
@@ -2612,7 +2613,8 @@ impl EditPredictionStore {
                     .uri(url.as_ref())
                     .header("Content-Encoding", "zstd")
                     .header(PREDICT_EDITS_MODE_HEADER_NAME, mode.as_ref())
-                    .header(PREDICT_EDITS_REQUEST_ID_HEADER_NAME, request_id.as_str());
+                    .header(PREDICT_EDITS_REQUEST_ID_HEADER_NAME, request_id.as_str())
+                    .header(PREDICT_EDITS_TRIGGER_HEADER_NAME, trigger.as_ref());
                 let builder = if let Some(preferred_experiment) = preferred_experiment.as_deref() {
                     builder.header(PREFERRED_EXPERIMENT_HEADER_NAME, preferred_experiment)
                 } else {