v0.9.0

Added

• Scene-based layer ordering — the cursor-chain / LayerOrderRegistry architecture is replaced by a scene model: LayerScene (single source of truth, commit-phase mutations, immutable plan()) + SceneSync (debounced walk + single-flight reorderLayers/applyEntryPriorities). Order is a function of committed state, derived from an anchor walk over the committed view tree.
• LayerStackController — native absolute-plan applier (MapMutationQueue-serialized) with a post-apply self-check surfaced in getDebugLayerDump() (appliedMatchesExpected, expectedUuids, appliedUuids, notInPlanCount).
• Deterministic fragment keys — frag:<owner>:<type> (SharedLayer/LayerMarker) and run:<anchor> (implicit type-runs).
• useSceneBusy() — reactive hook (exported) signalling that the layer-scene presenter has pending/in-flight ordering work (walk, sync, entry-priority commits, or unapplied mutations). Consumers can wire it to a loading indicator; re-renders only on true↔false transitions.
• SceneSync.subscribeBusy() / isBusy() — busy subscription for the scene presenter.
• Shared-layer extension hooks — useSceneFragmentUuid (standalone type-run fragment key), useSceneFragmentReady (grouped-entry readiness gate), and the fragmentUuidFor / runUuidFor deterministic identity builders, exported for third-party shared-fragment layer types.
• updateLayers batch API — LayerPath geometry/paint updates collapse into one native updateLayers call per frame (per-entry updateCoordinates batching), removing the per-line bridge churn on bulk re-render (e.g. zoom re-simplification).

Changed

• Fragment UUID scheme — shared-layer fragment UUIDs changed from __vtm_shared_<type>__<index> to frag:<owner>:<type> / run:<anchor>. Any code keying on the old strings must update.
• Create-phase performance — planWithResolved is now memoized per fragment/type-run, and LayerScene batches listener notification into one microtask flush, collapsing the many-entry create phase from O(N²) to ~O(N log N).

Removed

• useLayerOrder / createLayerOrderRegistry / LayerOrderRegistry — replaced by useLayerAnchor, useLayerEntry, useSceneUuidBinding, LayerScene, and SceneSync (all exported from src/index.tsx).
• Create-time positionIndex — the positionIndex param is no longer sent to native createLayer/createMarker. Within-fragment order is now applied via applyEntryPriorities using sparse priorities from PriorityAllocator.
• Synchronous LayerHelper.addLayer / removeLayer — deleted; use addLayerAsync / removeLayerAsync (the only layer-mutation API).
• SceneCommand / commandLog() — the replayable command log was removed; LayerScene.version() is the mutation signal.