Add PowerShell execution-region binding catalog

[Aaronontheweb]

Summary

• add the version-pinned PowerShell 7.6.4 execution-region receiver and parameter-set catalog
• prove aliases, positional and inline binding, ForEach-Object ScriptBlock array phases, and conservative receiver timing/cardinality
• fail closed for ambiguous identities, parameter sets, value conversions, platform-dependent options, and the optional ThreadJob module baseline
• pin the catalog with 100 focused cases and update the v0.3 implementation plan

Validation

• dotnet build -c Release --no-restore
• dotnet test -c Release --no-build --no-restore (2,025 passed)
• pwsh ./scripts/Add-FileHeaders.ps1 -Verify
• openspec validate v0-3-structured-shell-analysis --strict
• slopwatch on both modified C# files (0 findings)
• adversarial review: GO on frozen staged diff b3d4f60fbbea1a6176e8c798dee786865b8ce58a722db0f82fef88237dccecb0

This slice adds the internal catalog only. Parser execution-region emission remains the next v0.3 task.