Add snapshot pagination for persisted realtime history (#61480)

## What changed

Add experimental `thread/realtime/list` reads independent of turn pagination or a live runtime. Support session, observation-time, and event-ID filters, with ordering by observation time or committed position.

Keep cursor pagination within a fixed snapshot and expose positions for catching up on events committed later. Return `unsupported`, `pending`, or `ready` coverage so clients can distinguish unavailable history from events awaiting indexing. Limit fork reads to the child's own realtime history.

## Testing

Add SQLite tests for snapshot stability, late-event catch-up, cursor validation, and coverage tracking. Extend app-server tests to cover filtering, exact event lookup, and fork isolation.

GitOrigin-RevId: 8158df53f10d948ede4911654aa8adbc7297b258

sdk/python/src/openai_codex/generated/v2_all.py

@@ -6415,6 +6415,12 @@ class ThreadRealtimeClosedNotification(BaseModel):
     thread_id: Annotated[str, Field(alias="threadId")]
 
 
+class ThreadRealtimeCoverage(Enum):
+    unsupported = "unsupported"
+    pending = "pending"
+    ready = "ready"
+
+
 class ThreadRealtimeErrorNotification(BaseModel):
     model_config = ConfigDict(
         populate_by_name=True,
@@ -6538,6 +6544,11 @@ class ThreadRealtimeItemTranscriptDeltaNotification(BaseModel):
     thread_id: Annotated[str, Field(alias="threadId")]
 
 
+class ThreadRealtimeOrder(Enum):
+    observed_at = "observedAt"
+    position = "position"
+
+
 class ThreadRealtimeOutputAudioDeltaNotification(BaseModel):
     model_config = ConfigDict(
         populate_by_name=True,
@@ -12927,6 +12938,14 @@ class ThreadItemsListResponse(BaseModel):
     ] = None
 
 
+class ThreadRealtimeEntry(BaseModel):
+    model_config = ConfigDict(
+        populate_by_name=True,
+    )
+    item: ThreadRealtimeItem
+    position: Annotated[int, Field(ge=0)]
+
+
 class ItemThreadTimelineEntry(BaseModel):
     model_config = ConfigDict(
         populate_by_name=True,