[Feature] Configurable timezone for displayed timestamps (currently UTC-only)

Problem

Claude Code Desktop displays timestamps (session list, transcript headers, status line, etc.) in UTC with no way to override. For users not in UTC, this requires constant mental math to figure out when a session ran, when a tool call happened, etc.

Checked the settings reference — there's no timezone, locale, or tz field, and no documented env var (TZ, CLAUDE_TIMEZONE) that Claude Code respects.

Requested

Any one of these would solve it:

1. Respect the TZ env var (POSIX/IANA format, e.g. America/New_York) — Node-native, zero new config surface.
2. Add a timezone field to settings.json — explicit, discoverable.
3. Fall back to system timezone by default — what users would naturally expect on a desktop app.

Current Workaround

None. The only mitigation is mental subtraction (UTC−4 for EDT, UTC−5 for EST).

Environment

• Claude Code Desktop on Windows 11
• User timezone: America/New_York (EDT)