Non-main views (summary stats etc) don't actually sort when user clicks a sortable header

[paddymul]

Summary

Surfaced in code review of #739 by chatgpt-codex-connector:
#739 (comment)

makeStaticInfiniteDs in packages/buckaroo-js-core/src/components/BuckarooWidgetInfinite.tsx is the fake IDatasource wrapping pre-loaded DFData arrays (summary stats and friends) so non-main views can share the AG-Grid rowModelType: "infinite" with the main view. The change there in #739 keeps the grid mounted across df_display swaps — that part is the intended win.

But its getRows just slices the input array and calls successCallback:

getRows: (params: IGetRowsParams) => {
    const slice = data.slice(params.startRow, params.endRow);
    params.successCallback(slice, data.length);
}

params.sortModel is ignored.

Impact

Pre-#739, summary stats and other non-main views were rendered through AG-Grid's client-side row model (data_type: "Raw"), which sorted rows in memory automatically when the user clicked a sortable header. After #739 they use the infinite row model with this fake datasource, so:

• Sort UI on the column header still works (arrow flips, classes update)
• Rows do not reorder
• Net effect: clicking a sortable header on summary stats looks broken

Fix sketch

Sort the array inside getRows according to params.sortModel before slicing. Roughly:

getRows: (params: IGetRowsParams) => {
    const sm = params.sortModel;
    const sorted = sm.length === 0
        ? data
        : [...data].sort((a, b) => {
            for (const { colId, sort } of sm) {
                const av = a[colId], bv = b[colId];
                if (av === bv) continue;
                const cmp = av < bv ? -1 : 1;
                return sort === "desc" ? -cmp : cmp;
            }
            return 0;
        });
    params.successCallback(sorted.slice(params.startRow, params.endRow), data.length);
}

Mind: summary-stats rows often have mixed-type cell values (numbers, strings, nested objects, "—") — the comparator needs to handle that without throwing. Probably easiest to lean on lodash's _.orderBy for type-safe sorting.

Acceptance

• Click any sortable column header on the summary-stats view of a real notebook df — rows reorder.
• Sort indicator and order match the rendered rows.
• No regression on the main infinite view (which goes through getDs, not this fake datasource).

Notes

Originally identified during the #739 review. Doesn't block #739 itself, but should land before the next release that ships #739.