Feature: Show usage reset countdown timer in status line

Problem

Currently the status line shows usage percentage like:

Usage ███████████████░  92%

But there's no way to know when the usage will reset until you actually hit 100% and get rate limited. At that point, a countdown timer appears (e.g., "Retry in 2m 34s..."), but by then it's too late to pace yourself.

Proposal

Show the remaining time until usage resets directly in the status line, before hitting 100%:

Usage ███████████████░  92% (resets in 2h 13m)

Or alternatively:

Usage 92% · resets in 2h 13m

Why this matters

• Pacing: Users on Max plan can pace their usage if they know how much time remains. ("I've used 90% with 3 hours left — I should save some for later.")
• Planning: Helps decide whether to start a large task now or wait for a reset.
• Transparency: The rate limit countdown already exists when hitting 100%, so the server presumably knows the reset window. Exposing it earlier would be a natural extension.

Current behavior

• Before 100%: Only percentage shown, no time info
• At 100%: Countdown timer appears (1-second granularity), but only after being rate limited

Expected behavior

• Reset countdown visible at all times in the status line, updating in real time