Review fix: duplicate-name scan excludes only the edited child

Review round 1 (Codex gpt-5.6-terra) found: a case-only edit could
suppress the duplicate-name warning even when a DIFFERENT child
already carried the normalised name, because the edit path compared
only against the child's own old name. The scan now always runs on
the resulting state and excludes only the child being edited
(exclude_child_id), so case-only edits and stay-duplicated renames
warn like any other collision; renaming to your own name stays
warning-free when no other child holds the name. Tests: new
case-only-collision test, stay-duplicated rename assertion, and a
split self-rename test; suite at 848 passed.

custom_components/nestquest/children.py

@@ -74,16 +74,25 @@ def _validate_sort_order(value: object) -> int:
 
 
 async def _warn_on_duplicate_name(
-    database: NestQuestDatabase, display_name: str
+    database: NestQuestDatabase,
+    display_name: str,
+    *,
+    exclude_child_id: int | None = None,
 ) -> None:
     """Log a warning when ``display_name`` duplicates an existing child.
 
     Case-insensitive and whitespace-normalised on both sides.  The
     duplicate is still allowed — this only makes it visible; the log
     line names both rows so an accidental double-add can be found.
+    ``exclude_child_id`` removes the child being edited from the scan,
+    so an edit only warns when the result collides with a DIFFERENT
+    child's name — including case-only edits, where the self-comparison
+    would otherwise hide a real duplicate.
     """
     lowered = display_name.casefold()
     for child in await ChildrenDao(database).list_all():
+        if exclude_child_id is not None and child.id == exclude_child_id:
+            continue
         if child.display_name.strip().casefold() == lowered:
             LOGGER.warning(
                 "Child display name %r duplicates existing child %d "
@@ -142,9 +151,10 @@ async def edit_child(
     field raises: the DAO's update writes only provided fields and
     cannot express NULL, so a silent no-op would mask the caller's
     intent (see the module docstring).  A provided display name is
-    validated like create's and, when it duplicates a DIFFERENT child,
-    still allowed with a warning.  Raises ValueError when the child
-    does not exist.
+    validated like create's; the duplicate scan excludes only the child
+    being edited, so a case-only edit colliding with another child's
+    normalised name still warns.  Raises ValueError when the child does
+    not exist.
     """
     dao = ChildrenDao(database)
     existing = await dao.get(child_id)
@@ -154,8 +164,7 @@ async def edit_child(
     if display_name is not _UNSET:
         name = _validate_text(display_name, "display_name", required=True)
         assert name is not None
-        if name.casefold() != existing.display_name.strip().casefold():
-            await _warn_on_duplicate_name(database, name)
+        await _warn_on_duplicate_name(database, name, exclude_child_id=child_id)
         updates["display_name"] = name
     if colour is not _UNSET:
         value = _validate_text(colour, "colour")