Sync OpenAI Tasks guide with latest Docs callback-task retrieval flow

[Copilot]

Upstream Docs updated task retrieval guidance for OpenAI image callbacks, but this repo still documented a trace_id-first polling flow. This PR syncs the OpenAI Tasks integration guide to the current task_id-first model.

• Scope

  • Updated openai/docs/openai_tasks_api_integration_guide.md only.
  • Kept changes limited to content affected by recent Docs sync.

• Documentation sync: callback retrieval semantics

  • Clarified that callback-mode submit endpoints return task_id synchronously.
  • Reframed trace_id as optional/correlation-only instead of default retrieval path.
  • Updated id / trace_id field descriptions to match upstream wording.

• Documentation sync: examples

  • Changed single-task Python example from trace_id lookup to id lookup.
  • Updated end-to-end submit-and-poll example to:
    • remove generated trace_id
    • capture task_id from submit response
    • poll /openai/tasks using {"action":"retrieve","id": task_id}

submit = requests.post(
    f"{API}/openai/images/generations",
    headers=HEADERS,
    json={"model": "gpt-image-1", "prompt": "...", "callback_url": "..."},
).json()

task_id = submit["task_id"]

task = requests.post(
    f"{API}/openai/tasks",
    headers=HEADERS,
    json={"action": "retrieve", "id": task_id},
).json()

[Germey]

Superseded by new sync trigger; Copilot will open a fresh PR for the latest Docs state.