You have the mandate and a quarter to show it was real. The temptation is to write a strategy. Resist it. In the first 90 days, one shipped workflow beats a beautiful roadmap every time.
Ship one thing, involve the right three people
Pick a single high-volume, low-judgment workflow. Pull in one HR owner, one data or IT partner, and one person from legal or compliance early, not at the end. Deploy it to a real team, measure it against a baseline, and write down what broke.
Deliberately skip the enterprise platform decision, the center of excellence org chart, and the three-year vision deck. Those are Quarter Two problems. Quarter One is about proof, in production, that your People function can build.