addParticipant + updateParticipant used sortParticipantsByInitiative (stable
sort, tie-break = original array index). That destroyed manually-dragged tie
order when a drag moved a same-init pair — violated the slot-not-sort design
(docs/INITIATIVE_ORDERING.md: 'Re-slotting on add/edit must preserve
drag-established tie order').
Fix: new slotIndexForInit(list, init) returns splice index into the CURRENT
list (initiative-descending). addParticipant inserts there; updateParticipant
re-inserts only when initiative changed (unrelated edits keep slot — avoids
mid-round rotation dupes surfaced by the 100-round combat test).
Tests:
- turn.slot-not-sort.test.js: drag tie order survives add/edit (4 cases).
- static.no-sort.test.js: errs if .sort( added outside allowlist
(sortParticipantsByInitiative only). Verified by injecting a stray sort —
guard caught it.
