fix(timer): carry rounded minutes into the hour in humanDuration

[clawedassistant26]

What

humanDuration() in src/timer.mjs derives hours and minutes independently from the raw seconds:

const h = Math.floor(total / 3600);
const m = Math.round((total % 3600) / 60);

When the sub-hour remainder is in the last 30 seconds of a minute-that-completes-the-hour, m rounds up to 60 while h has not been incremented, so the output shows 60m, 1h 60m or 23h 60m instead of carrying into the hour.

Reproduce (before)

humanDuration(3599)  => "60m"      (want "1h")
humanDuration(7199)  => "1h 60m"   (want "2h")
humanDuration(86399) => "23h 60m"  (want "24h")
humanDuration(3570)  => "60m"      (want "1h")

This is user-facing in /timer off, /timer status and /timer log totals — a time-tracking surface that renders e.g. 1h59m59s as "1h 60m".

Fix

Round to whole minutes first, then split once so the carry happens in one place:

const minutes = Math.round(total / 60);
const h = Math.floor(minutes / 60);
const m = minutes % 60;

Tests

Added regression cases in test/timer.test.mjs (3599→1h, 3570→1h, 3569→59m, 7199→2h, 86399→24h). Reverting only the src/timer.mjs change fails exactly that one test; with the fix all timer tests pass. Full suite: 2277 pass / 0 fail / 337 skip.