[Bug]: Plan progress, background task rows, and "Ran N subagents" rows are never folded away

When a response finishes, its intermediate steps collapse behind a "Worked for …" row — except three kinds of rows, which always stay on screen: the plan progress chip ("… 3/3"), work rows from background tasks, and the "Ran N subagents" row.

Area: apps/web

Steps to reproduce

1. Send a prompt that makes the agent write a plan, run a background task, and spawn subagents.
2. Wait for the response to finish.

Expected behavior
Everything except the final message collapses behind the "Worked for …" row.

Actual behavior
The fold row and the final message appear, but the plan chip, the background task rows, and the "Ran N subagents" row are left scattered outside the fold.

Cause (from reading the code)
The folding code only collects rows that carry a turn id (the internal id that marks which turn a row belongs to). Background task rows have no turn id, plan rows are never considered at all, and the "Ran N subagents" row is skipped on purpose.

Impact: Cosmetic issue — the clutter stays permanently on any answer that used plans, background tasks, or subagents.

Version or commit: v0.0.34-nightly.20260823.1164; still present on main @ 31c1c5996.

Workaround
We patched our own deployment to collapse every row between the user message and the final answer, regardless of turn id. Spawned agents stay reachable from the Agents panel and by expanding the fold. Happy to share the diff.

Start in apps/web by locating the folding code that gathers rows carrying a turn id, then trace how plan progress, background task, and "Ran N subagents" rows are represented. Reproduce the described prompt flow and inspect the resulting row sequence. Done means all intermediate rows collapse behind the "Worked for …" row while the final message remains visible and the Agents panel still provides access to spawned agents.