fix(web): fold single trailing activity

[maria-rcks]

Single trailing activity rows could appear below the "Worked for ..." fold. This folds one ordinary trailing activity while leaving larger groups, failures, agent spawns, and compaction visible. Verified with 84 focused tests, web typecheck, targeted lint, and the real expand/collapse interaction.

Created with gpt-5.6-sol in T3 Code.

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Note

Low Risk
UI-only timeline folding logic with targeted unit and render tests; no API or data-path changes.

Overview
Settled turns no longer leave a lone successful tool row dangling below the final assistant message and the Worked for… fold.

deriveTurnFolds now treats one non-failing work entry immediately after the terminal assistant message as part of the fold (same hidden set as pre-terminal activity). Multiple trailing entries, failed tools, compaction, and agent-spawn rows still stay visible as trailing summaries.

Tests cover the folded single-trailing case and align the trailing-tool integration fixture with failed lifecycle so failures remain outside the fold.

^{Reviewed by Cursor Bugbot for commit 4c785d5. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Fix folding of single trailing activity in chat.deriveMessagesTimelineRows

Fixes the timeline row derivation so a single trailing activity folds correctly into the turn-fold row rather than producing extra rows. The test in MessagesTimeline.logic.test.ts now refactors the settled-error setup into a reusable typed input and asserts that a shortened timeline yields only the turn-fold row and terminal assistant row, with no trailing work toggle or assistant metadata row.

^{Macroscope summarized 4c785d5.}

[macroscopeapp]

Approvability

Verdict: Approved at 4c785d5

Macroscope's review found this PR approvable — This is a narrowly scoped web timeline fix that folds only a single ordinary trailing activity while preserving visibility for failures and larger groups. The production change is isolated and covered by focused tests, with no schema, deployment, security, billing, or configuration impact.

Notes:

• No code objects were reviewed. Approvability was decided on eligibility alone.

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Dismissing prior approval to re-evaluate 59ade45

Dismissing prior approval to re-evaluate 4c785d5