#22441: fix: force store for openai-responses providers

Fixes #21782 ## Summary - Force `store: true` for all `openai-responses` providers, not just direct OpenAI hosts. - Prevents `previous_response_id` failures on Azure/OpenAI-compatible endpoints when `store` defaults to false. ## Notes - Responses API multi-turn requires persisted items; Azure returns 400 when `store` is false. <!-- greptile_comment --> <h3>Greptile Summary</h3> Simplifies `shouldForceResponsesStore` to force `store=true` for all `openai-responses` API providers, removing the previous restriction to direct OpenAI hosts. This prevents 400 errors on Azure and OpenAI-compatible endpoints that require persisted items for multi-turn conversations. - The existing test at `src/agents/pi-embedded-runner-extraparams.e2e.test.ts:267-279` expects `store=false` for proxy URLs and will need to be updated - Comment on line 13 should be updated to reflect the new behavior (no longer limited to "direct" OpenAI) <h3>Confidence Score: 4/5</h3> - This PR is safe to merge after updating the test and comment - The logic change is straightforward and addresses a real bug with Azure/compatible endpoints. However, there's a test that will break and a comment that needs updating, which are easy fixes but should be addressed before merging. - Check that the existing test at `src/agents/pi-embedded-runner-extraparams.e2e.test.ts:267-279` is updated to match the new behavior _{Last reviewed commit: f3e1ad3} <!-- greptile_other_comments_section --> _{(2/5) Greptile learns from your feedback when you react with thumbs up/down!} <!-- /greptile_comment -->