fix(core): ensure otid exists when flushing buffered anthropic tool chunks Anthropic TOOL_USE buffering can emit buffered tool_call/approval chunks on content block stop before otid is assigned in the normal inner_thoughts_complete path. Ensure flush-time chunks get a deterministic otid so streaming clients can reliably correlate deltas. 👾 Generated with [Letta Code](https://letta.com) Co-authored-by: Letta <noreply@letta.com>