v0.9.4

Galaxy drag performance, a layout-busy state, and viewport history for GraphCanvas.

Changed

• GraphCanvas engine layouts now apply one frame after their inputs change, not during the
  same commit (#307). This lets the new busy state paint before a slow
  engine (for example orthogonal) blocks the main thread. Code or tests that read node
  positions immediately after rendering or after changing layout, nodes or edges must
  now wait: for data-layout-state="idle" on .graph-canvas, or for onLayoutStateChange
  to report 'idle'. While a new layout computes, the previous positions stay on screen. Before
  the first layout, nodes and edges without a position are hidden rather than stacked at the
  origin, so the first visible frame is the laid-out (and, with fitView, fitted) graph. If
  inputs change again before the deferred run starts, the stale run is dropped. An engine error
  still reaches the nearest error boundary.

Fixed

• GraphCanvas (layout="galaxy", live simulation) — dragging a node no longer stalls on
  larger graphs (#287). Each drag frame re-resolved overlaps around the
  dragged system with an all-pairs pass repeated up to 400 times: about 260 ms per frame at 252
  nodes and 30 s at 3000. Overlaps are now found through a spatial grid, only boxes that moved
  are re-checked, and a live frame spends a bounded amount of work on them, finishing any
  remainder over the next frames. A drag frame now costs about 1 ms at 252 nodes and under 10 ms
  at 3000. The settled layout, and static galaxyLayout() output, are unchanged.

Added

• GraphCanvas — layout busy state (#307).
  • Reporting: onLayoutStateChange and a data-layout-state root attribute report
    'computing' while an engine layout runs, 'simulating' while galaxy live simulation moves
    nodes, and 'idle' otherwise.
  • Indicator: a "Laying out…" status chip (role="status", aria-live="polite") appears
    once a layout has been busy for 150 ms. Turn it off with showLayoutIndicator={false}.
  • Exported type: GraphLayoutState.
  • Not included: running engines in a Web Worker.
• GraphCanvas — viewport history (#309).
  • onViewportDwell (with dwellMs, default 1500) fires once the viewport has been still
    after a user pan/zoom (drag, wheel, pinch, keyboard, toolbar +/-). It never fires
    mid-gesture or while inertia is still gliding.
  • onViewportNavigate reports moves the canvas or the app made, with a
    GraphViewportCause: center-on-select (with nodeId), fit (mount, toolbar,
    fullscreen or resize; layout is reserved) or imperative.
  • initialViewport replaces the mount fit and centring, for deep links and reloads.
  • setViewport(viewport, { animate, silent }) and getViewport() are on a new
    viewportRef handle and on useGraphCanvas(). silent suppresses onViewportNavigate,
    so restoring a history entry doesn't record a new one. animate is a 150 ms ease, a jump
    under prefers-reduced-motion.
  • Snapshots are in world coordinates (center, zoom, bounds).
  • New types: GraphViewportSnapshot, GraphViewport, GraphViewportCause,
    GraphViewportHandle, GraphSetViewportOptions.
• usePanZoom — optional onUserGesture('start' | 'change' | 'end') option and a
  getViewport() return value. Existing callers are unaffected.