Clarify that prompt features only categorize prompts, don't impact runs

[cedricvidal]

Original author: JaGord

Users confuse prompt features with something that affects run behavior. Add clarification in the UI that prompt features are metadata used to categorize prompts and filter runs during analysis.

[ahcrm-core]

Hi, I’d like to work on this. I plan to add a concise clarification in the Prompt Features UI that features are metadata used for categorization and analysis filtering and do not affect run behavior, with focused test coverage. Is the Prompt Features list page the preferred location, or should the clarification also appear in the task-level Prompt Features panel?