feat(graph): interactive drag, wheel zoom, pan, hover highlight (G2-G5)

[thetechjon]

Makes the noteser-graph fullscreen view feel like Obsidian by consuming the v1.3 interaction surface (L1-L4). Only public/plugins/noteser-graph/ and a new test under src/__tests__/ are touched; src/plugins (the platform) is untouched.

Behaviours

G2 — wheel zoom + drag pan. The svg declares panZoom: 'host', so the host owns the viewBox: wheel-zoom and dragging the background pan instantly with no worker round-trip. On settle the host emits one surface.transform {x,y,scale} event; the plugin reconstructs the viewport box (viewportFromTransform) and persists it under g2.viewport, so the viewport survives a reload. The nine manual zoom/pan buttons are deleted; a single Reset view button remains (net code removal).

G3 — node drag (pin/unpin). onPointerDown pins a node (the host auto-captures the pointer because the circle declares both down + move); onPointerMove drags it to payload.{x,y} (already svg user-space). The simulation reheats around pinned nodes (simulationStep skips integration for fixed nodes) and streams only the moved coordinates via ctx.patchSvgPositions({ viewId, patches }) each frame (L4 patch channel) — no full-tree re-emit, so a 500-node drag holds 60fps. A pinned node keeps a distinct ring; click a pinned node to unpin, or use Release pinned.

G4 — hover highlight. onPointerEnter/onPointerLeave dim every non-neighbour circle and brighten/thicken the hovered node's edges (hoverNeighbours). Recolor only — no re-layout, no patch channel.

G5 — click vs drag. A press that releases within ~4px and ~250ms (isTapGesture) is a click: a click on a free note node selects it and surfaces the open link; a click on a pinned node unpins it. A real drag never opens the note.

Platform events used

• L1 pointer: onPointerDown/Move/Up + automatic pointer capture (G3, G5)
• L2 wheel + host pan/zoom: VNodeSvg.panZoom:'host' + the surface.transform settle event (G2)
• L3 hover: onPointerEnter/Leave (G4)
• L4 patch channel: ctx.patchSvgPositions(...) + line.sourceId/targetId + circle.id (G3)

Known platform limitation

PluginCtx exposes no ctx.openNote(id) and SVG children cannot be a link VNode, so a true single-click programmatic open is not possible. G5 ships as click-vs-drag disambiguation that surfaces the existing wikilink:// open link on a genuine click. The existing wikilink open behaviour still works. Closing this fully would need a new ctx.openNote host hook (intentionally not added here — the platform is done).

Preserved

All G1 features (local graph, color groups, filters, force tuning, tags-as-nodes) and the sidebar backlinks panel are unchanged. Manifest bumped to v0.3.0 with interaction: { pointer, wheel, hover } on the fullscreen view.

Tests / verify

• New pure-helper tests in src/__tests__/noteserGraphPluginG2G5.test.ts: click-vs-drag threshold, pinned-node fixed-flag in the sim step, hover neighbour set, viewport round-trip.
• npm run lint clean, npx tsc --noEmit zero errors, npm test -- --ci green (225 suites / 2891 tests).

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