[FreeApophis]

Closes #925 and #981, shipped together as groomed so Funcky.Async consumers migrate once. Stacked on #1039 (base remove-option-from-boolean); retarget after #1037 and #1039 merge.

Decision (confirmed 30 Oct 2026): System.Linq.AsyncEnumerable instead of System.Linq.Async 7

#925 says "require System.Linq.Async [7.0.0, 8)". I started that way and two Merge tests failed on net8/net9: System.Linq.Async 7 is a facade over System.Linq.AsyncEnumerable that also depends on System.Interactive.Async, whose AsyncEnumerableEx.Merge(this IEnumerable<IAsyncEnumerable<T>>) wins overload resolution over Funcky's Merge(…, Option<IComparer<T>> comparer = default) because it needs no default argument. Every Funcky.Async 2.0 consumer calling sources.Merge() would silently get Ix's concurrent merge instead of Funcky's sorted one, and the alternative (a parameterless Funcky overload) turns that into a CS0121 ambiguity for everyone. On top, 7.0.0's dependency graph carries a vulnerable Microsoft.Bcl.Memory (NU1903, an error under CI's warnings-as-errors).

Funcky.Async therefore depends on System.Linq.AsyncEnumerable [10.0.6, 12) directly, the package that is the .NET 10 base class library LINQ; the shared sources compile identically on both sides and no Ix enters the graph. A consumer that still references System.Linq.Async 5 or 6 gets CS0433 on System.Linq.AsyncEnumerable (loud, and the fix is to upgrade that reference to System.Linq.Async 7, a facade over the same package, or drop it). The reasoning is recorded in Directory.Packages.props, the changelog and the async chapter. Confirmed by the maintainer on 30 Oct 2026.

#925

• SystemLinqAsyncAdapter, SystemLinqAsyncTestAdapter, AsyncGrouping, the Chunk(size) shim and every SYSTEM_LINQ_ASYNC branch (sources and tests) are gone; AdjacentGroupBy returns IGrouping everywhere, Grouping.cs is linked into Funcky.Async for that.
• CI matrix: floor 10.0.6 and newest 10.0.14 of System.Linq.AsyncEnumerable. Funcky.Async becomes 2.0.0.
• Funcky.Async's CompatibilitySuppressions.xml is empty now: all 36 suppressions were the IAsyncGrouping/IGrouping differences between the net10.0 forward asset and the others.

#981

• The twelve …Await/…AwaitWithCancellation operators and the …AwaitAsync/…AwaitWithCancellationAsync overloads of the eight terminal aggregations are removed (three files deleted, the rest trimmed, orphaned private helpers removed) together with their tests; the AwaitSelector test generator went with them.
• PublicAPI: 116 *REMOVED* lines per asset (net10.0/net11.0 of Funcky, all four groups of Funcky.Async), plus the 8 IAsyncGrouping signatures and Chunk(int) removed and the 8 IGrouping signatures added for Funcky.Async.
• AsyncEnumerableAwaitOperatorCodeFix keeps the CS0618 path and now also handles CS1061: it recognizes the call by its name, by the receiver being a type the replacement's first parameter accepts, and classifies delegate arguments by syntax and type (lambda arity, delegate invoke arity, method group arity). Named arguments or an argument it cannot classify leave the call alone. New test class AsyncEnumerableAwaitOperatorRemovedCodeFixTest mirrors the CS0618 cases.
• Changelog, async chapter and the package readme updated.

Verified locally: Release build of the solution with TreatWarningsAsErrors, Funcky.Test 1596/1596 (net11.0) and 1562/1562 (net10.0), Funcky.Async.Test 424/424 on net9.0 and net8.0 at 10.0.6 and at 10.0.14, Funcky.Analyzers.Test 262/262.

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