Adaptify.PureView 0.1.20

• • Aardvark.Build (>= 2.0.7 && < 2.1.0)
  • FSharp.Core (= 8.0.403)
  • FSharp.Data.Adaptive (>= 1.2.26 && < 1.3.0)

- perf: `AdaptiveFanout.zip` (positional, shorter-wins) is now properly incremental — folds both inputs' deltas in one pass and recomputes only affected positions (value change → O(#changes·log n); structural insert/remove → O((n−s)·log n) from the first shifted rank; shrink → tail removes), instead of re-materializing both full input states every tick.
- fix: a user helper returning `SceneAttribute` applied to a lifted model field now binds the helper's `aval<_>`-typed overload directly (`flowAttribute i.Flow`) instead of `AVal.map`-wrapping the plain overload into an unyieldable `aval<SceneAttribute>`. The plain↔aval overload swap (added for `Sg.VertexAttribute` in 0.1.18) now also fires for user helpers — the aval overload is found via FCS metadata, not just loaded-assembly reflection. Enables the idiomatic "static attribute existence, adaptive value" form.
- fix: nested-type static-member qnames no longer emit the CLR `+` separator (`HeapBuilders+Flow.attribute` → `HeapBuilders.Flow.attribute`, valid F#).
- fix: a top-level `match`/`if` on a lifted field that yields a scene-graph attribute in one branch but not another no longer emits malformed F# (`.IsNone` on a lifted aval, undefined builder); it raises a clear error — an sg's attribute *structure* is static (which attributes exist can't depend on an adaptive value, only their values can) — pointing to the static-attribute/adaptive-value helper form.
- (still deferred) the dead reference-impl modules remain compiled into the shipped lib (namespaced out of consumers' scope; correctness unaffected) — removal is a future cleanup.