You are splitting a solution excerpt into smaller parts for error review. You do
not judge correctness here.

## Question (context only)
{question}

## Excerpt to split (node {node_id}, depth={depth})
{node_excerpt}

## Task
Decide whether the excerpt is ATOMIC: a single claim, step or calculation that
would lose its meaning if split further. If it is atomic, return
{{"atomic": true, "parts": []}}.

Otherwise choose ONE boundary that separates the excerpt into two
self-contained pieces of reasoning (for example between two steps, cases or
paragraphs), preferably near the middle, and return the two pieces. The parts
must be copied VERBATIM from the excerpt: contiguous, in their original order,
nonempty, with no character added, removed, rewritten, summarized or
duplicated. Together, parts[0] followed by parts[1] must reproduce the whole
excerpt.

## Output
Return only one JSON object and nothing else:
{{"atomic": false, "parts": ["<first part, verbatim>", "<second part, verbatim>"]}}
or
{{"atomic": true, "parts": []}}
