Keep duplicate tasks off the human's list

[danielehrhardt]

Agents put the same thing on My tasks several times (H-154 = H-93, H-117 = H-116, COO roll-ups H-156/H-157/H-159 that only list open tickets).

• human_task_create, ask_human and request_approval check the open list (all agents and chats) and refuse a duplicate, naming the existing ticket.
• A decision found in a final answer is skipped when its title mentions an H-ref (status roll-ups), matches an open ticket, or matches one answered in the last 3 days.
• A reworded decision in the same chat keeps its ticket instead of replacing it.
• Matching: word overlap of the titles (EN/DE filler words dropped, numbers normalized), at least 3 shared words and 80 % of the shorter title.

Tests: bun test test/human-tasks.test.ts 24 pass; core suite 2002 pass, the same 6 fail on main without this change (folders, mods, maintenance, updates).