[codex-analytics] stop sending codex error subreason (#27060)

## Summary
- stop emitting `codex_error_subreason` on `codex_turn_event`
- remove the transient analytics fact plumbing that copied
`CodexErr::InvalidRequest(String)` into the event
- update analytics serialization coverage accordingly

## Why
`codex_error_subreason` is a free-form copy of `InvalidRequest(String)`,
including raw provider 400 bodies in some paths. That makes it unsafe as
an analytics field because it can carry user-derived or sensitive text.

## Validation
- `just fmt`
- `just test -p codex-analytics`

codex-rs/analytics/src/analytics_client_tests.rs

@@ -3318,7 +3318,6 @@ fn turn_event_serializes_expected_shape() {
             status: Some(TurnStatus::Completed),
             turn_error: None,
             codex_error_kind: None,
-            codex_error_subreason: None,
             codex_error_http_status_code: None,
             steer_count: Some(0),
             total_tool_call_count: None,
@@ -3391,7 +3390,6 @@ fn turn_event_serializes_expected_shape() {
                 "status": "completed",
                 "turn_error": null,
                 "codex_error_kind": null,
-                "codex_error_subreason": null,
                 "codex_error_http_status_code": null,
                 "steer_count": 0,
                 "total_tool_call_count": null,
@@ -4098,10 +4096,6 @@ async fn turn_lifecycle_emits_failed_turn_event() {
         payload["event_params"]["codex_error_kind"],
         json!("invalid_request")
     );
-    assert_eq!(
-        payload["event_params"]["codex_error_subreason"],
-        json!("unknown turn environment id `env-2`")
-    );
     assert_eq!(
         payload["event_params"]["codex_error_http_status_code"],
         json!(null)

codex-rs/analytics/src/events.rs

@@ -803,7 +803,6 @@ pub(crate) struct CodexTurnEventParams {
     pub(crate) status: Option<TurnStatus>,
     pub(crate) turn_error: Option<CodexErrorInfo>,
     pub(crate) codex_error_kind: Option<CodexErrKind>,
-    pub(crate) codex_error_subreason: Option<String>,
     pub(crate) codex_error_http_status_code: Option<u16>,
     pub(crate) steer_count: Option<usize>,
     pub(crate) total_tool_call_count: Option<usize>,

codex-rs/analytics/src/facts.rs

@@ -30,9 +30,6 @@ use codex_protocol::request_permissions::RequestPermissionsResponse;
 use serde::Serialize;
 use std::path::PathBuf;
 
-const INVALID_REQUEST_SUBREASON_MAX_BYTES: usize = 512;
-const INVALID_REQUEST_SUBREASON_TRUNCATION_SUFFIX: &str = "...";
-
 #[derive(Clone, Debug, PartialEq, Eq, Serialize)]
 pub struct AcceptedLineFingerprint {
     pub path_hash: String,
@@ -182,7 +179,6 @@ pub(crate) enum CodexErrKind {
 #[derive(Clone)]
 pub(crate) struct TurnCodexError {
     pub(crate) kind: CodexErrKind,
-    pub(crate) subreason: Option<String>,
     pub(crate) http_status_code: Option<u16>,
 }
 
@@ -190,26 +186,6 @@ impl TurnCodexError {
     fn from_codex_err(error: &CodexErr) -> Self {
         Self {
             kind: error.into(),
-            subreason: match error {
-                CodexErr::InvalidRequest(message) => {
-                    // InvalidRequest can contain raw provider response bodies, so bound the
-                    // analytics copy without changing the source CodexErr.
-                    let subreason = if message.len() <= INVALID_REQUEST_SUBREASON_MAX_BYTES {
-                        message.clone()
-                    } else {
-                        let truncated_len = message.floor_char_boundary(
-                            INVALID_REQUEST_SUBREASON_MAX_BYTES
-                                .saturating_sub(INVALID_REQUEST_SUBREASON_TRUNCATION_SUFFIX.len()),
-                        );
-                        format!(
-                            "{}{INVALID_REQUEST_SUBREASON_TRUNCATION_SUFFIX}",
-                            &message[..truncated_len]
-                        )
-                    };
-                    Some(subreason)
-                }
-                _ => None,
-            },
             http_status_code: error.http_status_code_value(),
         }
     }

codex-rs/analytics/src/reducer.rs

@@ -2470,7 +2470,6 @@ fn codex_turn_event_params(
         status: completed.status,
         turn_error: completed.turn_error,
         codex_error_kind: codex_error.map(|error| error.kind),
-        codex_error_subreason: codex_error.and_then(|error| error.subreason.clone()),
         codex_error_http_status_code: codex_error.and_then(|error| error.http_status_code),
         steer_count: Some(turn_state.steer_count),
         total_tool_call_count: Some(turn_state.tool_counts.total),