Support standalone named function call outputs (#39782)

## Why

External tool events may need to enter thread history without a preceding function call and therefore do not have a `call_id`.

## What changed

- Allow `function_call_output` items to omit `call_id` and carry optional `name` and `namespace` fields.
- Preserve named standalone outputs during history normalization and agent forks while retaining existing pairing behavior for outputs with a `call_id`.
- Accept, persist, and forward these outputs through `thread/inject_items`, and update the app-server schemas and documentation.

## Testing

- Cover paired and standalone JSON round trips, history normalization, agent forks, and injected thread history.

GitOrigin-RevId: a3258163a7dc93777c7c3023116fe204819bdbb0

codex-rs/ext/guardian-v2/src/async_scorer/extension_tests.rs

@@ -918,7 +918,9 @@ max_recent_non_user_entries = 8
         },
         ResponseItem::FunctionCallOutput {
             id: None,
-            call_id: "previous-call".to_owned(),
+            call_id: Some("previous-call".to_owned()),
+            name: None,
+            namespace: None,
             output: FunctionCallOutputPayload::from_text("README.md".to_owned()),
             internal_chat_message_metadata_passthrough: None,
         },
@@ -1174,7 +1176,9 @@ async fn contributor_includes_configured_transcript_images() -> Result<()> {
         },
         ResponseItem::FunctionCallOutput {
             id: None,
-            call_id: "previous-call".to_owned(),
+            call_id: Some("previous-call".to_owned()),
+            name: None,
+            namespace: None,
             output: FunctionCallOutputPayload::from_content_items(vec![
                 FunctionCallOutputContentItem::InputText {
                     text: "Screenshot captured.".to_owned(),
@@ -1386,7 +1390,9 @@ async fn contributor_samples_tool_calls_with_the_existing_luna_pool() -> Result<
         },
         ResponseItem::FunctionCallOutput {
             id: None,
-            call_id: "previous-call".to_owned(),
+            call_id: Some("previous-call".to_owned()),
+            name: None,
+            namespace: None,
             output: FunctionCallOutputPayload::from_text("README.md".to_owned()),
             internal_chat_message_metadata_passthrough: None,
         },
@@ -1662,7 +1668,9 @@ async fn contributor_sends_compacted_conversation_history_to_luna() -> Result<()
             },
             ResponseItem::FunctionCallOutput {
                 id: None,
-                call_id,
+                call_id: Some(call_id),
+                name: None,
+                namespace: None,
                 output: FunctionCallOutputPayload::from_text(format!(
                     "result evidence {index}: {}",
                     "signal ".repeat(1_000)

codex-rs/ext/guardian-v2/src/async_scorer/transcript.rs

@@ -228,7 +228,9 @@ impl TranscriptConfig {
                     (format!("tool {name} call"), arguments.clone())
                 }
                 ResponseItem::FunctionCallOutput {
-                    call_id, output, ..
+                    call_id: Some(call_id),
+                    output,
+                    ..
                 }
                 | ResponseItem::CustomToolCallOutput {
                     call_id, output, ..
@@ -287,6 +289,7 @@ impl TranscriptConfig {
                     ("tool web_search call".to_owned(), text)
                 }
                 ResponseItem::AdditionalTools { .. }
+                | ResponseItem::FunctionCallOutput { call_id: None, .. }
                 | ResponseItem::ImageGenerationCall { .. }
                 | ResponseItem::ToolSearchCall { .. }
                 | ResponseItem::ToolSearchOutput { .. }

codex-rs/ext/guardian-v2/src/async_scorer/transcript_tests.rs

@@ -40,7 +40,9 @@ fn transcript_keeps_conversation_and_configured_sources() {
         },
         ResponseItem::FunctionCallOutput {
             id: None,
-            call_id: "call-1".to_string(),
+            call_id: Some("call-1".to_string()),
+            name: None,
+            namespace: None,
             output: FunctionCallOutputPayload::from_text("Workspace inspected.".to_string()),
             internal_chat_message_metadata_passthrough: None,
         },
@@ -459,7 +461,9 @@ fn transcript_truncates_tool_results_using_standard_budget() {
         },
         ResponseItem::FunctionCallOutput {
             id: None,
-            call_id: "call-1".to_owned(),
+            call_id: Some("call-1".to_owned()),
+            name: None,
+            namespace: None,
             output: FunctionCallOutputPayload::from_text(output),
             internal_chat_message_metadata_passthrough: None,
         },
@@ -596,7 +600,9 @@ fn transcript_omits_media_payloads_and_keeps_readable_content() {
         },
         ResponseItem::FunctionCallOutput {
             id: None,
-            call_id: "call-1".to_string(),
+            call_id: Some("call-1".to_string()),
+            name: None,
+            namespace: None,
             output: FunctionCallOutputPayload::from_content_items(vec![
                 FunctionCallOutputContentItem::InputText {
                     text: "Screenshot captured.".to_string(),