gate_bars(user_id, note_type) resolves the block bar and, for notes and
tasks, the overlap floor from kb_gate_* settings, with the old constants
as defaults. Fail-open on an unreadable value; a block bar clamps at 0.80
and the overlap floor at 0.70 and never above the bar. Five fields in
Settings beside the duplicate-report floors.
CLAIM_LEASE stays a constant, with the reason written at it: a per-user
lease would make one shared task live to one reader and dead to another.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
