Timestamps always show AM/PM on Linux (Bun ignores system locale) #28804

Description

Timestamps in the session view always display in 12-hour AM/PM format on Linux, regardless of system locale settings.

Steps to Reproduce

1. Set LC_TIME=da_DK.UTF-8 (or any 24-hour locale like en_GB.UTF-8)
2. Run opencode and check session timestamps
3. Times show 8:23 AM instead of 08.23 or 08:23

Root Cause

Bun's JavaScriptCore ignores POSIX locale environment variables (LC_TIME, LANG) when undefined is passed to toLocaleTimeString(). It defaults to en-US (12h) regardless of system settings.

Upstream: oven-sh/bun#7386 (open since Dec 2023)

Expected Behavior

Timestamps should respect the system locale (LC_ALL > LC_TIME > LANG).

Environment

• OS: Linux (Ubuntu 24.04)
• Locale: LC_TIME=da_DK.UTF-8, LANG=en_GB.UTF-8
• OpenCode: dev branch