Summary:

• pass an explicit GPT-5 model into Nous Portal provider parity tests so they do not initialize AIAgent with an empty/default model
• skip Discord history backfill when a channel-like object does not expose history, matching the regression covered by fix(discord): skip history backfill when channel lacks .history #26301
• add a small regression test for the missing-history Discord path

Tests:

• python -m pytest -o addopts= tests\run_agent\test_provider_parity.py::TestDeveloperRoleSwap::test_developer_role_via_nous_portal tests\run_agent\test_provider_parity.py::TestBuildApiKwargsNousPortal::test_includes_nous_product_tags tests\run_agent\test_provider_parity.py::TestBuildApiKwargsNousPortal::test_uses_chat_completions_format -q --tb=short
• python -m pytest -o addopts= tests\gateway\test_discord_free_response.py::test_fetch_channel_context_returns_empty_when_channel_lacks_history -q --tb=short
• python -m pytest -o addopts= tests\e2e\test_discord_adapter.py -q --tb=short
• python -m ruff check gateway\platforms\discord.py tests\gateway\test_discord_free_response.py tests\run_agent\test_provider_parity.py
• git diff --check