Enable ghost_commit feature by default (#6041)

## Summary
- enable the ghost_commit feature flag by default

## Testing
- just fmt

------
https://chatgpt.com/codex/tasks/task_i_6904ce2d0370832dbb3c2c09a90fb188

Author: jif-oai

codex-rs/core/src/features.rs

@@ -284,7 +284,7 @@ pub const FEATURES: &[FeatureSpec] = &[
         id: Feature::GhostCommit,
         key: "ghost_commit",
         stage: Stage::Experimental,
-        default_enabled: false,
+        default_enabled: true,
     },
     FeatureSpec {
         id: Feature::WindowsSandbox,

codex-rs/core/tests/suite/otel.rs

@@ -1,3 +1,4 @@
+use codex_core::features::Feature;
 use codex_protocol::protocol::AskForApproval;
 use codex_protocol::protocol::EventMsg;
 use codex_protocol::protocol::Op;
@@ -101,6 +102,7 @@ async fn process_sse_emits_failed_event_on_parse_error() {
 
     let TestCodex { codex, .. } = test_codex()
         .with_config(move |config| {
+            config.features.disable(Feature::GhostCommit);
             config.model_provider.request_max_retries = Some(0);
             config.model_provider.stream_max_retries = Some(0);
         })
@@ -141,6 +143,7 @@ async fn process_sse_records_failed_event_when_stream_closes_without_completed()
 
     let TestCodex { codex, .. } = test_codex()
         .with_config(move |config| {
+            config.features.disable(Feature::GhostCommit);
             config.model_provider.request_max_retries = Some(0);
             config.model_provider.stream_max_retries = Some(0);
         })
@@ -193,6 +196,7 @@ async fn process_sse_failed_event_records_response_error_message() {
 
     let TestCodex { codex, .. } = test_codex()
         .with_config(move |config| {
+            config.features.disable(Feature::GhostCommit);
             config.model_provider.request_max_retries = Some(0);
             config.model_provider.stream_max_retries = Some(0);
         })
@@ -243,6 +247,7 @@ async fn process_sse_failed_event_logs_parse_error() {
 
     let TestCodex { codex, .. } = test_codex()
         .with_config(move |config| {
+            config.features.disable(Feature::GhostCommit);
             config.model_provider.request_max_retries = Some(0);
             config.model_provider.stream_max_retries = Some(0);
         })
@@ -288,6 +293,7 @@ async fn process_sse_failed_event_logs_missing_error() {
 
     let TestCodex { codex, .. } = test_codex()
         .with_config(move |config| {
+            config.features.disable(Feature::GhostCommit);
             config.model_provider.request_max_retries = Some(0);
             config.model_provider.stream_max_retries = Some(0);
         })
@@ -333,6 +339,7 @@ async fn process_sse_failed_event_logs_response_completed_parse_error() {
 
     let TestCodex { codex, .. } = test_codex()
         .with_config(move |config| {
+            config.features.disable(Feature::GhostCommit);
             config.model_provider.request_max_retries = Some(0);
             config.model_provider.stream_max_retries = Some(0);
         })
@@ -438,6 +445,7 @@ async fn handle_response_item_records_tool_result_for_custom_tool_call() {
 
     let TestCodex { codex, .. } = test_codex()
         .with_config(move |config| {
+            config.features.disable(Feature::GhostCommit);
             config.model_provider.request_max_retries = Some(0);
             config.model_provider.stream_max_retries = Some(0);
         })
@@ -497,6 +505,7 @@ async fn handle_response_item_records_tool_result_for_function_call() {
 
     let TestCodex { codex, .. } = test_codex()
         .with_config(move |config| {
+            config.features.disable(Feature::GhostCommit);
             config.model_provider.request_max_retries = Some(0);
             config.model_provider.stream_max_retries = Some(0);
         })
@@ -566,6 +575,7 @@ async fn handle_response_item_records_tool_result_for_local_shell_missing_ids()
 
     let TestCodex { codex, .. } = test_codex()
         .with_config(move |config| {
+            config.features.disable(Feature::GhostCommit);
             config.model_provider.request_max_retries = Some(0);
             config.model_provider.stream_max_retries = Some(0);
         })
@@ -619,6 +629,7 @@ async fn handle_response_item_records_tool_result_for_local_shell_call() {
 
     let TestCodex { codex, .. } = test_codex()
         .with_config(move |config| {
+            config.features.disable(Feature::GhostCommit);
             config.model_provider.request_max_retries = Some(0);
             config.model_provider.stream_max_retries = Some(0);
         })