fix(core): keep placement drafts out of undo history

[Aymericr]

Summary

• exclude fresh placement roots and their descendants from scene history snapshots until finalization
• remove transient references from parents, roots, and collections so both Zundo and external commit subscribers see a valid document snapshot
• add a regression proving draft motion emits no history and finalization produces one undoable, redoable step

Test plan

• bun run check
• bun run check-types
• bun run test
• bun run build

---

Note

Medium Risk
Touches core scene history and commit boundaries used by undo and sync; behavior change is scoped to isNew placement flows but incorrect subtree/collection filtering could affect undo or host patches.

Overview
Placement drafts (metadata.isNew) no longer enter undo stacks or scene commit snapshots until the user finalizes placement.

sceneHistorySnapshotFromState now strips every isNew root and its full descendant subtree from history snapshots, and cleans parent children, rootNodeIds, and collections so Zundo and subscribeSceneCommits see a consistent document without transient nodes. Edits while still in draft mode produce no commits or undo steps; clearing isNew records one step whose before omits the subtree and whose current includes the finalized placement (undo/redo removes or restores the whole subtree).

A regression test covers create → draft motion → finalize → undo/redo.

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Marking live nodes new deletes history

High Severity

sceneHistorySnapshotFromState drops any node once metadata.isNew becomes true. Paths that first create a normal node and then set isNew (door/window paste) therefore emit a second local commit and undo step shaped like a delete: before still has the node, current does not. External commit subscribers and undo can then remove a just-pasted node.

 

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