[release plan] Wrong trigger of SDK generation for old release plan

For this [PR](https://github.com/Azure/azure-sdk-for-go/pull/27232), it is from the release plan [35305](https://azsdk-releaseplan-dashboard-hveph5aqhhcfhtgu.westus-01.azurewebsites.net/?releaseplan=35305). The plan originally targeted 2026-05-15-preview version and the SDK PR's previous status is correct. But after this [PR](https://github.com/Azure/azure-rest-api-specs/pull/46149) merged, the SDK generation was triggered again target the given release plan, which result to the wrong API version and spec commit ID. What's the full rule of the SDK generation trigger? What's the full rule of the release plan? Do we have any official doc for that?

Start by comparing release plan 35305 with the SDK generation triggered after azure-rest-api-specs PR 46149, using Azure SDK PR 27232 to identify the prior correct status. Trace the documented or implemented trigger and release-plan rules, then verify whether the generated API version and spec commit ID match the plan. Done means the trigger behavior and official documentation requirements are clearly established.

Written by the indexing model from the issue text.