Allow inline annotations on plans

Problem

When reviewing a generated plan, requesting changes requires restating the step and surrounding context in chat. This is verbose and error-prone.

Proposal

Allow users to select plan text or a plan step and attach an inline annotation. When submitted, annotations should be sent to the agent anchored to the exact plan location.

Desired UX

• Add comments directly to a line, selection, or step.
• Collect multiple annotations before requesting a revision.
• Preserve annotations across plan revisions, marking anchors stale when needed.
• Show which annotations were addressed and which remain unresolved.

Benefit

This would make plan iteration faster and more precise, without requiring users to retype context.

首先跟踪生成计划的审查流程，以及修订请求如何发送给代理。梳理选择计划文本或步骤、提交多个批注以及渲染修订后计划的入口。完成的标准是：批注可以在不同修订版本之间进行锚定、保留或标记为过时，并显示为已处理或未解决。