[denyrt]

Summary

• Add an immutable PgnGame model with tags, initial FEN, coordinate moves and a declared result.
• Support mainline PGN import/export using canonical SAN, with result validation and structured diagnostics.
• Explicitly reject comments, NAGs, variations and unsupported variants.
• Add integration tests, package-consumer coverage, performance benchmarks and API documentation.

Validation

dotnet restore ChessRealms.Engine.slnx --locked-mode
dotnet build ChessRealms.Engine.slnx -c Release --no-restore
dotnet test ChessRealms.Engine.slnx -c Release --no-build --filter "TestCategory!=Deep"
pwsh -NoProfile -File scripts/Verify-SolutionStructure.ps1
git diff --check

All checks passed: 1,528 tests, no build warnings or errors.

Additional validation:

• Built .nupkg and .snupkg artifacts and validated them with Verify-Package.ps1.
• Passed Test-PackageConsumer.ps1 against the local package.
• Completed 60 benchmark scenarios across core operations, game API, SAN and PGN, plus the allocation probe.
• Checked local documentation links and new-file whitespace.

Deep tests were not run. Benchmarks used short in-process runs and do not establish production latency guarantees. The package-consumer check required execution outside the sandbox after a NuGet access-denied failure.

Compatibility and risks

• PGN import supports one game's tags and mainline with canonical SAN; annotated PGN files are explicitly rejected.
• The declared PGN result is separate from ChessGame.Outcome. Restoration does not infer resignation, timeout or draw-claim details.
• PGN processing allocates model and replay data. Import followed by ToGame() performs two replays; further optimization remains possible.
• The package version remains 1.1.0; the planned 1.2.0 bump is a separate step.

Checklist

• The change is focused on one logical purpose.
• Tests were added or updated when behavior changed.
• Documentation was updated when required.
• Relevant local validation passed, or limitations are explained above.
• No credentials, personal data, or unintended generated files are included.