Fix Friday-dependent retrospective tests #1944

Problem

Two RetroCapability tests derive their fixture date from the real clock and expect a same-day retrospective to produce retro not due.

Production behavior intentionally forces a retrospective every Friday after 14:00 UTC, so those tests fail whenever CI runs during that window:

• reports not due when a recent retrospective log exists
• checks log/ under stateRoot, not teamRoot, for existing retrospectives

This blocks unrelated PRs even though the implementation is behaving as designed.

Fix

Freeze time within the RetroCapability test scope to a known non-Friday instant, restore real timers afterward, and add explicit coverage for the Friday-after-14:00 UTC behavior so both contracts remain deterministic.