fix(sessions): paginate OpenAI conversations session reads

[Neonstudio28]

Summary

OpenAIConversationsSession.get_items(limit=N) was forwarding the local session limit as the Conversations API page size. Provider page-size limits could therefore reject otherwise valid session reads before pagination ran. This change lets the existing async iterator own provider pagination, applies the session cutoff locally, and preserves chronological ordering.

Test plan

• uv run pytest tests/memory/test_openai_conversations_session.py tests/memory/test_session_limit.py -q — 56 passed (16 existing asyncio deprecation warnings).
• uv run ruff check src/agents/memory/openai_conversations_session.py tests/memory/test_openai_conversations_session.py — passed.
• git diff --check — passed.
• Targeted mypy and pyright checks for the changed runtime file — passed.
• The repository verification wrapper completed formatting and linting, then stopped at pre-existing repository-wide type errors in sandbox/voice/optional-extension modules. The full test target also hit unrelated optional-environment and restricted-temp-directory failures; the changed session tests pass independently.

Issue number

Closes #4757

Checks

• I've added new tests, if relevant
• I've run .agents/skills/code-change-verification/scripts/run.sh
• I've confirmed all verification steps pass
• If using Codex, I've run /review before submitting this PR

[Copilot]

🟢 Approval recommended

No unresolved review comments remain, and all reviewers assessed it as ready.

Pull request overview

Fixes OpenAI Conversations session pagination by applying limits locally while preserving chronological ordering.

Changes:

• Delegates provider pagination to the async iterator.
• Adds regression coverage for local limits and ordering.

File summaries

File	Summary
tests/memory/test_openai_conversations_session.py	Verifies local limiting and pagination behavior.
src/agents/memory/openai_conversations_session.py	Applies limits after provider pagination.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0
• Review effort level: Lite

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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Bound the provider page size for small limits

When callers use a small positive history limit (for example, get_items(limit=1)) on conversations containing large item payloads, omitting limit makes the paginator fetch its full default page before this loop can break. Previously the request fetched no more than the requested number of items; retain a provider-safe capped page size so oversized limits paginate but the common small-window path does not download unnecessary conversation data and add avoidable latency.

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