Folding two assistant turns that reuse a provider id (llama.cpp-style constant ids) leaves
both calls in tool_calls, but the {id: uid} union kept only the later uid, so the first
occurrence lost its identity. The id now maps to a list of uids, one per occurrence in
tool_calls order (merge_tool_call_uids); index_tool_call_uids pairs each call with its own
occurrence, so a following result still pairs with the nearest call. Provider ids are never
rewritten. Persisted and restored as-is (the JSON map accepts list values).
Reported by @andrexibiza on #126307.
d9808867c7