Phase 551: post-Phase-550 whiteboard authoring interaction queue refresh

[ExplodingUFO]

Context

Phase 550 / PR #224 records the first whiteboard primitive Cookbook screenshot implementation gate on top of the stacked Phase 547-549 model, renderer-adapter, and persistence-decision work. That stack is currently blocked behind the required review on PR #200, but the next authoring wave still needs to be split before any public drawing tool, pointer coordinator, toolbar UX, eraser behavior, or persisted whiteboard primitive claim is attempted.

AsterGraph now has internal whiteboard primitive model/projection/policy/visual-proof evidence in the stacked PR series, but it still does not have React Flow-style whiteboard authoring parity. The next step should be another docs/tests-only queue refresh that turns the remaining authoring pressure into small, dependency-aware issues with explicit write sets.

Scope

Create a bounded post-Phase-550 whiteboard authoring interaction queue refresh:

• inspect the current Phase 547-550 roadmap entries and stacked PR boundaries;
• identify the smallest next tracker-backed slices for public drawing tool activation, pointer gesture capture, authoring toolbar/Cookbook UX, eraser-on-primitive behavior, and any later persistence/schema work;
• create GitHub and Beads follow-up issues for the selected next slices with priorities, dependencies, and parallelism notes;
• update EN/ZH React Flow parity roadmap docs with Phase 551 plus the new follow-up rows;
• add focused docs tests that fail if the post-Phase-550 authoring wave is still implicit or TBD;
• preserve the stack ordering behind PR Add whiteboard primitive screenshot proof gate #224 and do not merge this before Phase 550.

Out of scope

No runtime behavior changes, no public API changes, no pointer coordinator edits, no toolbar implementation, no eraser implementation, no persistence/schema changes, no renderer rewrite, no screenshot manifest expansion, no UI redesign, no retained API removal, and no full React Flow whiteboard parity claim.

Dependency / stacking

This issue should be implemented as a stacked docs/tests branch on top of feature/phase-550-whiteboard-cookbook-screenshot-gate / PR #224 and must not merge before Phase 550. It should not disturb the existing blocked stack behind PR #200.

Acceptance criteria

• EN/ZH parity docs record Phase 551 with this GitHub issue and matching Beads ID.
• The docs convert post-Phase-550 authoring pressure into concrete tracker-backed follow-up rows with GitHub and Beads IDs, priorities, write sets, dependencies, and parallelism guidance.
• Follow-up rows explicitly separate public tool activation, pointer gesture capture, toolbar/Cookbook UX, eraser behavior, and persistence/schema work instead of bundling them into one broad whiteboard implementation.
• Focused docs tests guard the Phase 551 queue in both locales and fail if the next authoring wave remains TBD or implies full React Flow whiteboard parity.
• Verification includes the focused Phase 551 roadmap-doc test, the full ReactFlowParityRoadmapDocsTests suite, the full AsterGraph.Demo.Tests project, and git diff --check.