Review feedback (PR #2284) flagged that the merge-rules wording was
ambiguous: "every item has a `code` or `id` field" could reasonably
be read as "each item individually has at least one of the two",
allowing arrays to mix `code` and `id` across items.
The resolver has always required all items share the *same* identifier
key (all `code`, or all `id`). Mixed arrays fall through to append —
intentional, because mixing identifier keys within one array is a
schema smell and any guess about which key should merge creates a
worse trap than the append-fallback.
Clarified in three places:
- Merge-rules table in customize-bmad.md: "every item shares the
**same** identifier field"
- `code`/`id` convention paragraph: "pick **one** convention ... and
stick with it across the whole array"
- Resolver docstring and `_detect_keyed_merge_field` docstring:
explicit note that mixed arrays fall through with rationale
No behavior change.
80ba89eb52