fix(design): persist pointer-driven layer reorders

[steve8708]

Fixes Layers-panel reorder drops that arrive with an empty dataTransfer payload during pointer-driven Chromium drags.

• fall back to the authoritative same-window drag state
• exercise the reorder with Playwright pointer events
• verify the reordered layers survive reload

Validation: git diff --check passed. Focused runtime tests could not run because workspace dependencies are not installed.

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Review Details

Incremental Code Review — Previous Comment Resolved

The latest commit changes the helper declarations to non-exported declarations with explicit value/type re-exports:

• canUseActiveDragStateForDrop remains a named runtime export
• LayersPanelMoveIntent remains a type-only export
• The new Vitest import remains valid
• No application behavior or drag/drop logic changed

Two independent review agents found no confirmed regressions. One verified the new test import and another verified the explicit exports preserve the module API; direct TypeScript validation was also reported as successful.

The previously open comment requesting these exports has been verified fixed and resolved.

Risk: Standard; this is a module-export/testability adjustment with no runtime behavior change.

🧪 Browser testing: Skipped — the dev server was unavailable while workspace setup was still installing dependencies. The change is export-only and does not alter user-facing behavior.