test(show): pin the timestamp expectation to en-US/UTC like the formatter

[vicnaum]

Problem

formatConversationAsMarkdown renders timestamps with toLocaleString('en-US', { timeZone: 'UTC' }) (#120, #130), but the test in test/show.test.ts still builds its expectation with a bare toLocaleString(), i.e. the host's locale and timezone. The two only agree on en-US / UTC hosts, so the suite passes on CI and fails for anyone running it locally elsewhere:

Europe/Warsaw:  expected "9/19/2025, 7:34:29 PM", formatter produced "9/19/2025, 5:34:29 PM"
de_DE on UTC:   fails on the locale format

Fix

Format the expectation the same way the code does. One-line test change, no runtime change.

Verified passing under TZ=Europe/Warsaw, TZ=America/New_York and TZ=UTC, including LC_ALL=de_DE.UTF-8.

🤖 Generated with Claude Code

https://claude.ai/code/session_01L7qt58cTm5rFNfV38EQfEN

[obra]

Verified and landing. Thank you — this is a real portability bug and the diagnosis is exactly right.

formatConversationAsMarkdown pins timestamps at src/show.ts:97:

const timestamp = new Date(msg.timestamp).toLocaleString('en-US', { timeZone: 'UTC' });

and the expectation used a bare toLocaleString(). Those agree only on an en-US/UTC host, which is what CI happens to be — so the suite was green for everyone who could run it and red for everyone who couldn't.

Confirmed with a negative control, because a test change that passes everywhere proves nothing on its own:

base 28f0933a, TZ=Europe/Warsaw  ->  1 failed | 21 passed
PR   6854e8d5, TZ=Europe/Warsaw  ->  22 passed

Then across the environments the fix targets — TZ=UTC, TZ=America/New_York, and TZ=UTC LC_ALL=de_DE.UTF-8 — all 22 pass. No CI ran on the fork branch, so that local matrix is standing in for it.

One note, not a change request. The expectation now mirrors the implementation's exact call, so if someone changes the formatter's locale the test follows silently rather than failing. The alternative — asserting the literal "9/19/2025, 5:34:29 PM" — would catch that, at the cost of breaking whenever Node's ICU data shifts its formatting. For a timestamp render I think you've picked the right side of that trade; I'm flagging it only so the next person knows it was a choice.