git:20261027.bf64f38 to git:20261030.bc682ba

2 added, 2 removed. Audit A to A.

# Nino.Immutable: file map

> Read when: reading or changing the System.Collections.Immutable formatters (package Nino.Immutable).

netstandard2.0 and net8.0 (trimmable, NativeAOT compatible) library, packed as `Nino.Immutable`: formatters for the

eight immutable collections, registered with `[assembly: NinoFormatter]` so generated code and the runtime resolver

- bind them. Writes the bytes of the matching mutable collection. `audit-core` audits it; the root CLAUDE.md's

- "Machine code" rules (building a runtime's own objects) apply to the tree builders.

+ bind them. Writes the bytes of the matching mutable collection. `audit-core` audits it; the

+ tree builders follow `runtime-internals` (building a runtime's own objects).

```

Nino.Immutable.csproj targets, the Nino.Core reference (-p:NinoCoreTfm=netstandard2.0 / 2.1 picks a build),

System.Collections.Immutable on netstandard2.0, links Nino.Core's Internal/ObjectTypes.cs

ImmutableFormatters.cs the [assembly: NinoFormatter] list and the formatters: ImmutableArray (as T[], wrapped

without a copy), ImmutableList, ImmutableHashSet, ImmutableSortedSet, ImmutableQueue,

ImmutableStack, ImmutableDictionary, ImmutableSortedDictionary

HashTrees.cs ImmutableDictionary / ImmutableHashSet built directly as their tree through mirror classes

(DictionaryTree, SetTree), checked at startup, the builder's Add otherwise

SortedTrees.cs ImmutableSortedDictionary / ImmutableSortedSet built as their AVL tree in one pass from

items in order (SortedDictionaryTree, SortedSetTree)

Properties.cs [module: SkipLocalsInit]

```

## Rules for these files

- Read paths reach Nino.Core only through its public and `CompilerServices` API (`NinoEffectiveSettings` for the

frozen settings); `ObjectTypes.cs` is the one file compiled in.

- The mirror classes must match the fields of every System.Collections.Immutable version users may have (1.5 to

10.0 share them); `Usable` falls back to the builders when the layout check fails, and `tests/Nino.RuntimeTests`

has a `FastPaths` row for `HashTrees.Usable` and `SortedTrees.Usable`, so a runtime that falls back fails there.