[teamleaderleo]

Bead: cx-v9k2f (part 1 of 2; the app's lanes view follows in a second PR)

Problem

Leo, 2026-10-13: about 25 lanes sat idle for hours unnoticed, some dead on out-of-credit errors. acpmux decides each session's status dot (indicator), but nothing says how long a session has been in that state or why a turn failed. A daemon restart mid-turn also wrote a failed turn_result without recording it as the last turn, so that session read as idle.

Change

• Every session summary (_acpmux/watch, session_changed, _acpmux/sessions) carries lane = {state, since, error}. acpmux decides it once next to indicator, from the summary's own fields:
  • working since its turn started;
  • input while a permission or question waits;
  • idle since its last turn ended, or since it was created;
  • failed with the last turn's errorText;
  • lost when the agent process is gone without an answer.
  • A closed session has no lane.
• Peer sessions get it too, and it's re-decided when a peer goes unreachable (views::decide replaces the three separate indicator writes).
• Both outcome_unknown paths (a daemon restart, or a host that never got the prompt) now call record_last_turn. Those sessions read failed with the reason.
• restart_marks_unknown_outcome moves to tests/hub_integration/restart.rs, because hub_integration.rs was at its 1500-line cap.
• The lastTurn key list is views::LAST_TURN_KEYS, so hub/turns.rs (over the god-file limit on base) does not grow.

Verification

• Red at b8305e5 (tests only), hosted --filter lanes::: test result: FAILED. 0 passed; 5 failed on Linux and on macOS. Every lane test panicked because summaries had no lane.
• Green on 7076fa6 (base 541435d), hosted --filter lanes:: and --filter restart_marks_unknown_outcome: lint (linux), test (linux) and macOS lint and tests pass.
  • One run's release-path dogfood artifacts / build aarch64-apple-darwin failed; the other run built the same SHA. That job is not part of this change.
• Green again on fresh-merge head e8d8c24 (both filters): lint (linux) and test (linux) pass.
  • Earlier, at 5099ccd, the macOS hosted tests passed, and the peer test passed on 492bd45 (Linux).
  • The PR's own checks are all green on 7076fa6, including the macOS daemon tests and the same-tree daemon tests.
• crash_ratchet.py: ok.

Changelog

none

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[github-actions]

Not verified: macOS jobs did not run: compile and app tests were skipped on 52af7b59a5; ci-status is green without them.

CI passes on 52af7b59a5 (run 38555649642 attempt 1).
macOS jobs did not run: compile and app tests were skipped: Fast static checks skipped (the macos job needs both to succeed). Re-run CI once they pass, before merging.

Written by scripts/ci/classify_failures.py (ci-failure-attribution.yml); signatures are its SIGNATURES table. A machine verdict is the runner's fault, not this PR's; yours means the failing file is one this PR changes, also red on main that main's latest full suite fails the same way, seen on other PRs that it failed on another pull request's run lately.