[menes97]

Fixes #17

Grouping moves clashes from Results into Groups, but several export paths read only Results, so grouped clashes were silently left out. Following the issue's suggestion:

• NwcClashBcfExporter gets Save(string, IEnumerable<NwcClashTest>, string) and Write(Stream, IEnumerable<NwcClashTest>, string). They write every test into one archive: a topic per group and a topic per ungrouped clash. The existing Write(Stream, NwcClashTest, string) now calls the new Write with its one test, so its output is unchanged.
• NwcDocument.ExportClashBcf (both overloads), NwcAssembly.ExportClashBcf and NwcClashMatrix.SaveBcf pass their tests to these overloads. The CLI's --clash-bcf goes through ExportClashBcf, so --clash-group together with --clash-bcf now exports every clash.
• NwcClashMatrixCell.Clashes returns ExecutedTest.AllClashes, and SaveJson lists AllClashes, so the clashes array agrees with clashesCount.

Ungrouped tests export the same topics as before. I left NwcGridSystem alone: it reads only Results when annotating grid locations, which is a separate behaviour.

Tests (ClashGroupingTests): each groups five clashes into two groups and one ungrouped clash.

• Document_ExportClashBcf_IncludesGroupedClashes checks that NwcDocument.ExportClashBcf(Stream) writes 3 topics.
• Assembly_And_Matrix_ExportClashBcf_IncludeGroupedClashes checks the same through NwcAssembly.ExportClashBcf and NwcClashMatrix.SaveBcf.
• Matrix_ClashesAndJson_IncludeGroupedClashes checks that Clashes has 5 items, and that the SaveJson cell has clashesCount 5 and 5 entries in clashes.

All three fail without the change (1 topic, 1 clash). dotnet build NwcIO.slnx succeeds, and NwcIO.Tests passes locally: 242 passed, and 2 skipped because they need private Navisworks files (.NET 10.0.400 on Windows, with global.json pinned down to it temporarily; not committed).

🤖 Generated with Claude Code

[mahach666]

Changes requested: the intended fix is useful, but the inline comment below describes a regression reproduced against the reviewed head and the unchanged base. Please address it and add the indicated regression test before merging.

Finding: Keep existing calls with an empty collection source-compatible.

[mahach666]

[P2] Keep existing calls with an empty collection source-compatible

Adding a second public collection overload makes this existing C# call ambiguous:

NwcClashBcfExporter.Save("empty.bcfzip", []);

A separate consumer project compiles against the current main/base but fails against this PR with CS0121: IEnumerable<NwcClashResult> versus IEnumerable<NwcClashTest>. The new Write overload similarly breaks Write(stream, []).

Please use a distinct method name for exporting a collection of tests, or an internal helper for the document/assembly/matrix callers, so existing public calls continue to compile. Add a consumer compilation check covering the empty collection.