feat(plugins): v1.3 L2+L3+L4 — wheel, host pan/zoom, hover, position-patch channel

[thetechjon]

Round 2 of the v1.3 interaction surface, building on the merged L1 (pointer events + interaction manifest opt-in + rAF coalescing + HF budget). Ships L2, L3, and L4 together because all three edit the same platform files (PluginVNode.tsx, PluginHost.ts, protocol.ts, the surface adapters) — splitting them would mean three PRs conflicting over the same code.

L2 — wheel + host-owned pan/zoom (plan 2.2, 2.7 Cost 2)

• onWheel on VNodeSvg + VNodeBox. WheelEventPayload { deltaX, deltaY, x, y, ctrlKey }; x/y in the surface coordinate space (svg user-space via inverse CTM, box element-local). High-frequency → rides L1's coalescing, gated on interaction.wheel.
• Wheel listeners are non-passive only for interactive surfaces, so preventDefault can stop page scroll; a plain svg/box attaches no wheel listener and scrolls normally.
• VNodeSvg.panZoom: 'host' — the host owns the viewBox transform: drag-pan (surface pointer) and wheel-zoom mutate the rendered <svg> directly (no worker round-trip, 60fps) and emit exactly ONE surface.transform { x, y, scale } on gesture settle (pointerup, or a 150ms wheel-idle debounce). surface.transform is a reserved event name on the existing host:vnodeEvent envelope — not a new envelope.

L3 — hover (plan 2.2, 2.3)

• onPointerEnter / onPointerLeave on circle/rect/svg/box. HoverEventPayload { target, x, y }. High-frequency → coalesced, gated on interaction.hover.

L4 — position-patch channel (plan 2.7 Cost 2, 2.8)

• New worker→host envelope worker:patchSvgPositions { viewId?, panelId?, patches: {id,x,y}[] } on the WorkerToHost union + isWorkerToHost. Subject to MAX_ENVELOPE_BYTES; the host sanitises the patch shape.
• The host applies patches by mutating cx/cy on mounted SVG circles + the matching endpoint of any connected edge line (keyed via data-node-id / data-edge-source / data-edge-target), with NO React re-render. New SDK method ctx.patchSvgPositions(...).

Why ship together

All three are platform-layer changes to the same five files. The HF gate also had to grow from L1's single pointer flag into a per-kind gate (pointer/wheel/hover), which touches sendVNodeEvent + every surface adapter — a shared change all three depend on.

Notes

• Reuses L1's rAF coalescing — no second coalescing layer. HF dispatches now carry an interaction kind; an unset kind defaults to pointer so L1 behaviour + tests are unchanged.
• v1.2 + L1 plugins keep working: every new prop is optional; no-interaction manifests never get wheel/hover/patch paths.
• public/plugins/noteser-graph/ (G2/G3/G4) untouched — separate PR.
• Deviations recorded in docs/plugins-v1.3-impl-notes.md.

Tests

• npm run lint clean, tsc --noEmit zero errors, full Jest suite green (2869 passed, no flake).
• New unit tests: wheel payload + coords, hover enter/leave coalescing, per-kind HF gating, surface.transform fires once on pan settle + once after wheel-idle debounce, worker:patchSvgPositions validate + oversized reject, host applies a patch to the mounted svg without remounting the React tree.

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