GPT-5.6 Terra vs Grok 4.5 for code review

Review this function. Context you can rely on, because it is validated upstream: `customers` and `outcodes` are always arrays; every customer object has a `postcode` property that is either a string or null; postcodes are stored either with or without the space ('SW1A 1AA' or 'SW1A1AA'); the required behaviour is to return the customers whose outward code matches one of `outcodes`, case-insensitively. function filterByOutcode(customers, outcodes) { const wanted = new Set(outcodes.map(o => o.trim().toUpperCase())); return customers.filter(c => { const pc = (c.postcode || '').trim().toUpperCase(); if (pc.length < 5) return false; const outward = pc.includes(' ') ? pc.split(' ')[0] : pc.slice(0, -3); return wanted.has(outward); }); } Give your review. If there are defects, list them by severity with the input that triggers each one. If there are none, say so plainly and briefly — do not manufacture a defect to look thorough, and do not dress a style preference up as a bug.