A prompt goes stale when a decision it depended on changed. We flag it, quote the cost to refresh it, and leave the choice to you.
You may have already pasted that prompt and built on the result. Silently rewriting it would put your plan and your codebase out of sync without telling you — which is the exact failure we exist to prevent.
We trace which prompts read from the section you edited and mark only those.
Ready means unlocked and unused. In use means you pasted it and are building. Done means you ran the verification list. Outdated means a dependency moved. Locked means a prerequisite is not finished.