attribution: make summary percentages sum to 100

The summary computed AI/Human/Mixed percentages by independent integer division, so they drifted from a coherent whole — e.g. one line each of AI, Human, and Mixed rendered 33% / 33% / 33% = 99%. Apportion with the largest-remainder (Hamilton) method across all four buckets (including uncommitted, which shares the 100% but is shown only as a count) so the visible figures stay coherent.