An LLM that rewrites a file must see all of it

// before: page clipped to fit the prompt, model output overwrites the file
prompt.push(block('existing-page', page.slice(0, 30_000)));

// after: refuse rather than truncate
if (page.length > MAX_CHARS) throw new Error(`${path}: too large to rewrite safely`);
prompt.push(block('existing-page', page));