[FEATURE]: Desktop: user message hover timestamps should include the date, not just the clock time #44936

Problem

In OpenCode Desktop, hovering a user message shows a tooltip with only the clock time — no date, ever.

That means for any message not sent today there is no way to tell when it was actually written: yesterday's messages, last week's, or a month ago all look identical. Reopening older sessions makes this especially confusing, because the conversation reads as if everything happened today.

The duration shown for agent responses is useful and worth keeping as-is — but for user messages the missing piece is the absolute point in time.

Expected behavior

A message timestamp should let me distinguish at least today / yesterday / earlier:

• Minimum: include the date alongside the time in the hover tooltip (e.g. 2026-08-22 14:32 or locale-equivalent)
• Nicer: smart relative labels such as Today 14:32, Yesterday 09:10, Aug 12, with the full absolute date available on closer inspection (e.g. hovering the label itself)

Environment

• App: OpenCode Desktop 1.18.21
• OS: Microsoft Windows 11 Education, 25H2, build 26200.8875