Sisco/tiny preprocessor integration

[dsisco11]

Summary
This PR begins the TinyTokenizer → TinyAst transition using Strategy A: ship a new NuGet package id TinyAst while keeping the compiled assembly name and namespaces (TinyTokenizer / TinyTokenizer.Ast) unchanged for compatibility.

What Changed

• Packaging: Updated TinyTokenizer/TinyTokenizer/TinyTokenizer.csproj to:
  • Publish as PackageId=TinyAst / Title=TinyAst
  • Pin AssemblyName=TinyTokenizer and RootNamespace=TinyTokenizer to preserve runtime/type identity
  • Refresh description/tags to match “TinyAst” positioning
• Docs: Updated install instructions to point to TinyAst:
  • TinyTokenizer/README.md now includes a “Name Transition” section explaining:
    • install TinyAst now
    • namespaces remain TinyTokenizer.* for now
    • namespaces will migrate to TinyAst.* in a future major release
  • TinyTokenizer.wiki/Getting-Started.md uses dotnet add package TinyAst
• Planning: Added a phased migration checklist (package rename now, namespace migration later) in project.todo

Validation

• dotnet build -c Release
• dotnet test -c Release --no-build (1509 tests passed)
• dotnet pack -c Release --no-build -o .\nupkg_test /p:PackageVersion=0.0.0-local produced TinyAst.0.0.0-local.nupkg

Notes / Follow-ups

• Phase 2 is intentionally out-of-band: deprecate TinyTokenizer on nuget.org and stop publishing new TinyTokenizer versions (per decision), pointing users to TinyAst.
• CI workflow naming still uses PROJECT_NAME: TinyTokenizer in build.yml; it’s cosmetic, but can be updated in a follow-up PR.