Phase 551: whiteboard authoring queue refresh

[ExplodingUFO]

Summary

• record Phase 551 as the post-Phase-550 whiteboard authoring interaction queue refresh in both parity-roadmap locales
• add tracker-backed follow-up rows for Phases 552-556 covering activation, pointer capture, authoring toolbar/Cookbook UX, eraser behavior, and persistence decision
• add focused roadmap-doc coverage that guards the queue IDs, no-runtime boundary, stack ordering, and no full whiteboard parity claim

Stack / Merge Order

• Base: feature/phase-550-whiteboard-cookbook-screenshot-gate / PR Add whiteboard primitive screenshot proof gate #224
• This PR must not merge before Phase 550 / PR Add whiteboard primitive screenshot proof gate #224 and the earlier review-blocked stack land.
• It is docs/tests only: no runtime behavior, public API, pointer coordinator, toolbar, eraser, persistence/schema, renderer, screenshot-manifest, or UI behavior changes.

Verification

• dotnet test tests\AsterGraph.Demo.Tests\AsterGraph.Demo.Tests.csproj -c Release --filter "FullyQualifiedName~ParityRoadmapDocs_RecordPhase551WhiteboardAuthoringQueueRefreshInBothLocales" --verbosity minimal (1 passed)
• dotnet test tests\AsterGraph.Demo.Tests\AsterGraph.Demo.Tests.csproj -c Release --filter "FullyQualifiedName~ReactFlowParityRoadmapDocsTests" --verbosity minimal (51 passed)
• dotnet test tests\AsterGraph.Demo.Tests\AsterGraph.Demo.Tests.csproj -c Release --verbosity minimal (294 passed)
• dotnet build AsterGraph.sln -c Release -v:minimal (0 warnings, 0 errors)
• git diff --check (exit 0; LF-to-CRLF notices only)

Closes #225