forge-vesting — add test verifying pause() and unpause() shift start_time correctly and tokens accrue only for active time

[Austinaminu2]

Summary

unpause() shifts start_time forward by the pause duration:

let delta = now.saturating_sub(config.paused_at);
config.start_time = config.start_time.saturating_add(delta);

There is no test verifying this shift produces correct vesting amounts. If the shift is wrong, paused time would count toward vesting which is incorrect.

Tasks

• Initialize with cliff=0, duration=1000, total=10_000, at t=0
• At t=200, pause (should have 2_000 vested, 8_000 remaining)
• At t=400, unpause (paused for 200s — start_time shifts to 200)
• At t=600, assert vested = 10_000 * (600-200)/1000 = 4_000 (200s active pre-pause + 200s active post-resume)
• Call claim() at t=600 and assert it returns 4_000
• At t=1200 (equivalent to 1000 active seconds), assert fully_vested == true

Labels: testing, forge-vesting