Emit per-track summary `console.warn` for missing `dataTooltip` field references

**Context** After the first render pass, a single summary `console.warn` lists all missing fields for that track, not per data point. `src/tooltips/resolve.ts` silently substitutes missing fields as empty strings (which is correct behaviour at the per-cell level), but authors get no feedback when a `dataTooltip` template references a field the adapter never produced. This is a common foot-gun when authoring against an unfamiliar data source: the tooltip renders blank cells and the author has no breadcrumbs to the cause. **Task** Implement a per-track missing-field accumulator in the tooltip resolver and emit one summary `console.warn` per track, not per data point. **Scope:** * In `src/tooltips/resolve.ts` (or a helper), track the set of field paths that resolved to `undefined` while rendering any tooltip on a given track during a render pass. * After the render pass completes (or on the next animation frame — whichever is cheaper), emit a single `console.warn` of the form: `"[protvista-uniprot] Track <groupId>/<trackId>: dataTooltip references unknown fields: <field>, <field>, …"`. The warning fires once per track per render pass, not per data point. * Don't warn when the field resolves to a legitimate empty string / `null` — only when the field *path* doesn't exist on any of the track's data points. * Integrate the accumulator with both `kind: fields` and `kind: markdown` authoring forms. * Add a unit test in `src/tooltips/__spec__/resolve.spec.ts` that: (a) renders a tooltip template referencing three unknown fields across ten data points, and (b) asserts `console.warn` was called exactly once with all three field names. * Reinstate the deleted spec material in `specs/config-approach.md`: the Edge Cases row and the acceptance criterion. **Notes:** Keep the allocation/accounting path on the hot render path cheap — a per-track `Set<string>` populated during field resolution, flushed once per render pass, should be sufficient. No observable behaviour change for correctly-authored configs.