Vouch request: fix for #4187 (post-rewind context invites a second rewind call)

[tjboudreaux]

Hi — asking to be vouched per CONTRIBUTING.md so I can open a PR for a fix I have ready.

What I'd like to contribute

Fix for #4187 (post-rewind context invites a second rewind call, which then fails with an unactionable No active checkpoint.).

The branch is ready on my fork: tjboudreaux:fix/rewind-report-checkpoint-closed (diff vs main).

Summary of the change (details in the issue):

• Frame the rewind-report custom message with a checkpoint-complete notice (new prompts/system/rewind-report-context.md) so the post-rewind turn knows the checkpoint is CLOSED and doesn't re-call rewind.
• Make the no-active-checkpoint rewind error self-recovering (tells the model to continue, not retry).
• Document close-on-success in prompts/tools/rewind.md.
• Contract tests: framed-report assertions in agent-session-checkpoint-rewind-branch.test.ts, a RewindTool error-contract test, and a containment fix in checkpoint-rpc-qa.ts.
• Includes a one-line organize-imports fix for test/task/worktree.test.ts that was breaking bun check on main (pre-existing; happy to split it out if you'd rather).

bun check passes (ts + rs), bun test test/agent-session-checkpoint-rewind-branch.test.ts passes (2 pass / 14 expects), changelog updated under [Unreleased] → Fixed.

I also added independent evidence to #4173 (the replay-side hardening) from a captured 400 session — this fix addresses the context shape that manufactured the wasted rewind call in that same session.

If vouched, I'll open the PR immediately. Thanks!

[can1357]

!vouch @tjboudreaux Tyvm!