fix(turn): log reorder + deathSave (BUG-7)

reorderParticipants returned log:null → handler skipped logAction → drag
invisible in combat log, no undo payload. Now returns
log:{ message, undo:{ participants, turnOrderIds, currentTurnParticipantId }}.
App.js handleDrop calls logAction on logged reorders.

Found second gap: deathSave also returned null log (both branches).
Fixed — message + undo (participants snapshot).

Added logging contract test (turn.logging.test.js):
- all mutating ops logged (start/next/pause/add/remove/toggle/hp/deathsave/
  condition/reorder/end)
- no-ops return null log (same-id, cross-init, cross-pointer blocks)
- undo payloads valid + restore prior state
- documents addParticipants + updateParticipant gaps (null log, intentional)

235 tests green.

shared/turn.js

@@ -477,6 +477,8 @@ function deathSave(encounter, participantId, saveNumber) {
   if (!participant) throw new Error('Participant not found.');
   const currentSaves = participant.deathSaves || 0;
   const newSaves = currentSaves === saveNumber ? saveNumber - 1 : saveNumber;
+  const name = participant.name;
+  const undo = { participants: encounter.participants || [] };
 
   if (newSaves === 3) {
     // Mark dying — caller waits for animation, then calls removeParticipant.
@@ -485,7 +487,10 @@ function deathSave(encounter, participantId, saveNumber) {
     );
     return {
       patch: { participants: updatedParticipants },
-      log: null,
+      log: {
+        message: `${name} failed 3 death saves — dying`,
+        undo,
+      },
       isDying: true,
     };
   }
@@ -493,7 +498,14 @@ function deathSave(encounter, participantId, saveNumber) {
   const updatedParticipants = (encounter.participants || []).map(p =>
     p.id === participantId ? { ...p, deathSaves: newSaves } : p
   );
-  return { patch: { participants: updatedParticipants }, log: null, isDying: false };
+  return {
+    patch: { participants: updatedParticipants },
+    log: {
+      message: `${name} death save: ${newSaves}/3`,
+      undo,
+    },
+    isDying: false,
+  };
 }
 
 // TOGGLE_CONDITION — verbatim from ParticipantManager.toggleCondition
@@ -553,7 +565,17 @@ function reorderParticipants(encounter, draggedId, targetId) {
   const newTargetIndex = participants.findIndex(p => p.id === targetId);
   participants.splice(newTargetIndex, 0, removedItem);
   const turnUpdates = syncTurnOrder(participants); // 1-list: always mirror
-  return { patch: { participants, ...turnUpdates }, log: null };
+  return {
+    patch: { participants, ...turnUpdates },
+    log: {
+      message: `${removedItem.name} reordered before ${(participants.find(p => p.id === targetId) || {}).name || targetId}`,
+      undo: {
+        participants: encounter.participants || [],
+        turnOrderIds: encounter.turnOrderIds || [],
+        currentTurnParticipantId: encounter.currentTurnParticipantId ?? null,
+      },
+    },
+  };
 }
 
 // END_ENCOUNTER — verbatim from InitiativeControls.confirmEndEncounter