Squad stamps dates in UTC, so team files and logs show tomorrow's date in US evenings #2457

Found in the Claude Code end-to-end test for epic #2438 (fresh repo, dev build, 2026-11-10).

What happens: on a US evening (2026-11-09 local), Squad stamped team.md, member histories and the session log 2026-11-10. The coordinator noticed: "the files are stamped 2026-11-10, a day after today's date … the tools appear to use UTC time." The decision entry itself used the local date, so one session mixed both.

Why it matters: dates in team files and logs read as wrong to the user, and entries from one session can disagree.

Suggested fix: use the local date for human-facing stamps (or always UTC, with a marker), consistently across tools and templates.