fix(turn): log addParticipants + updateParticipant (logging gaps)

addParticipants + updateParticipant returned log:null → invisible in
combat log. Contract test caught them. Now both return
log:{ message, undo:{ participants }}.

App.js handlers wired (handleAddAllCharacters, handleUpdateParticipant,
handleInlineInitiative) — call logAction on logged mutations.

Logging contract now complete: every mutating combat op produces a log
entry. No gaps. turn.logging.test.js proves it.

238 tests green.

shared/tests/turn.logging.test.js

@@ -166,23 +166,38 @@ describe('Logging undo payloads', () => {
   });
 });
 
-describe('Logging: gaps (currently unlogged mutations)', () => {
-  // Document current behavior. addParticipants + updateParticipant return
-  // null log → invisible in combat log. May be intended (bulk/no-op) or bug.
+describe('Logging: addParticipants + updateParticipant', () => {
   let e;
   beforeEach(() => {
     e = enc([p('a', 10), p('b', 7)]);
   });
 
-  test('addParticipants returns null log (bulk gap?)', () => {
+  test('addParticipants logs', () => {
     const r = addParticipants(e, [p('c', 3)]);
-    // Currently null. Document so decision is explicit.
-    expect(r.log).toBeNull();
+    expectLogged(r);
   });
 
-  test('updateParticipant returns null log (edit gap?)', () => {
+  test('updateParticipant (same slot) logs', () => {
     const r = updateParticipant(e, 'b', { name: 'B' });
-    // Currently null. Document so decision is explicit.
-    expect(r.log).toBeNull();
+    expectLogged(r);
+  });
+
+  test('updateParticipant (init change) logs', () => {
+    const r = updateParticipant(e, 'b', { initiative: 5 });
+    expectLogged(r);
+  });
+
+  test('addParticipants undo restores prior list', () => {
+    const orig = e.participants.map(p => p.id);
+    const r = addParticipants(e, [p('c', 3)]);
+    const restored = { ...e, ...r.log.undo };
+    expect(restored.participants.map(p => p.id)).toEqual(orig);
+  });
+
+  test('updateParticipant undo restores prior participant', () => {
+    const orig = e.participants.map(p => p.id);
+    const r = updateParticipant(e, 'b', { name: 'B' });
+    const restored = { ...e, ...r.log.undo };
+    expect(restored.participants.map(p => p.id)).toEqual(orig);
   });
 });