Assert empty dataZoom preserves in-window raw stack values

Copilot suggested using raw axis dimensions for empty mode. A temporary verification showed that change turns raw y values for in-window stacked points into NaN, even though their stack result remains visible. Preserve the current implementation and cover that invariant explicitly.

Constraint: mapDimensionsAll(axisDim) includes both raw value and stack result dimensions for stacked series.

Rejected: Apply Copilot empty-mode suggestion | it corrupts raw values for in-window stacked points.

Confidence: high

Scope-risk: narrow

Directive: Do not special-case empty mode to mapDimensionsAll without preserving raw stacked values.

Tested: ./node_modules/.bin/jest --config test/ut/jest.config.cjs --coverage=false test/ut/spec/component/dataZoom --runInBand

Tested: npm run checktype

Tested: ./node_modules/.bin/eslint test/ut/spec/component/dataZoom/AxisProxy.test.ts

Tested: git diff --check -- test/ut/spec/component/dataZoom/AxisProxy.test.ts