[jogibear9988]

Description

Rewriting a DWG containing Solid3D, Region or CadBody can lose imported ACIS geometry or its wireframe/revision data. The inline reader returns before consuming the complete modeler record, binary ASM payloads are not recognized, and R2013+ output does not write the AcDs geometry section.

This preserves the existing SAT/SAB/ASM payload bytes through DWG conversions, reads the rest of the modeler record at the correct position, and writes the geometry's AcDs data and handle indexes for R2013+. It uses master's public modeler GUID API and modeler templates, retaining material handle references alongside their raw mapping values.

Tasks done in this PR

• Serialize inline SAT and binary modeler data and preserve points, wires, silhouettes, material mappings and revision metadata.
• Write R2013+ AcDs geometry records with schema/data/handle indexes and read their data headers in local-offset order.
• Add 14 regression cases: six source-version sample cases each converted to six target versions, SAT/ASM and wireframe roundtrips across six versions, and two DWG-to-DXF GUID cases.

Related Issues / Pull Requests

Extracted from #1316, source commit 52af836f. This PR contains one implementation commit on current master (90c6f871); it can be reviewed and merged independently. The aggregate PR #1316 remains unchanged and continues to hold the other fixes. Large-payload blob paging is a separate follow-up retained there.

The source behavior comes from acad-ts c4ecf35b, 319474b1 and 887fc2bc.

Notes for reviewer

A reproducible case is loading an existing samples/sample_AC1027.dwg, writing it with DwgWriter, then reading the result and comparing every modeler entity's AcisData by handle. ModelerGeometryWriterTests.SamplePayloadsSurviveVersionConversions performs this check for 36 source/target combinations. The synthetic tests also verify inline payloads, wireframe coordinates and GUID preservation through a subsequent DXF conversion.

Validation on this isolated branch:

• dotnet test src/ACadSharp.Tests/ACadSharp.Tests.csproj -f net9.0 --filter FullyQualifiedName~ModelerGeometryWriterTests: 14 passed.
• Full .NET 9 suite: 2,512 passed, 2 skipped, 3 failed. The failures are the previously observed ArcTests.CreateFromBulgeTest, ArcTests.GetCenter, and the culture/scientific-format case in DimensionStyleTests.GetLinearMeasurementText.
• Library builds for net8.0, net9.0, net10.0, net48, netstandard2.0 and netstandard2.1.
• git diff --check passes.

These are library roundtrip/build results; independent ODA conversion has not been run for this standalone PR. ACIS payload preservation does not provide a modeling engine.

AI-assisted port and extraction, with source comparison, isolated regression testing and review of the resulting diff.