The v2 timeline rendered every tool call as its own raw row; main's
tool-group collapsing (generated "Ran N commands and changed M files"
summaries, the live "Running <program>" pill for the active tool run,
and the "+N previous log entries" clamp for mixed groups) never made it
into the v2 row model.

Ported the work-live/work-toggle row kinds and group summarization into
the v2 derive, keyed on v2 item types (command_execution, file_change,
file_search, dynamic_tool, subagent) and runId lifecycle instead of v1
activities. Expanded groups keep the branch's richer per-entry detail
rows (V2ItemInspector) — only the collapsed presentation converges on
main.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>