forge-stream — add test verifying get_claimable() returns 0 immediately after withdraw() with no time passing

[Austinaminu2]

Summary

get_claimable() is a lightweight view function but there is no test verifying it returns 0 immediately after a full withdraw() call with no additional time passing. This is the most common polling pattern for UIs — check claimable, withdraw, check claimable again to confirm zero.

Tasks

• Create a stream, advance time by 100s
• Assert get_claimable() returns rate * 100
• Call withdraw()
• Without advancing time, assert get_claimable() returns 0
• Advance time by another 50s
• Assert get_claimable() returns rate * 50 (only newly accrued)
• Verify this matches get_stream_status().withdrawable

Labels: testing, forge-stream

[Emins25]

Implemented and opened PR for this issue: #344

Summary:

• added a polling-flow regression test around get_claimable()
• verifies claimable resets to 0 immediately after withdraw()
• verifies only newly accrued tokens become claimable after more time passes