chore: remove unused NFP nesting code

Delete OpenNest.Engine/Nfp (AutoNester, BottomLeftFill, NfpCache,
SimulatedAnnealing, INestOptimizer, PlacedPart, SequenceEntry), the Core
InnerFitPolygon, and the NestPhase.Nfp member. None had callers outside the
folder: console --autonest and MCP autonest_plate call engine.Nest(), not
AutoNester.

Drop the Nfp cases from NestPhaseExtensionsTests, fix the --autonest help
text, and update CLAUDE.md. NoFitPolygon stays; BestFit pair evaluation
still uses it.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

OpenNest.Tests/Engine/NestPhaseExtensionsTests.cs

@@ -6,7 +6,6 @@ public class NestPhaseExtensionsTests
     [InlineData(NestPhase.Linear, "Trying rotations...")]
     [InlineData(NestPhase.RectBestFit, "Trying best fit...")]
     [InlineData(NestPhase.Pairs, "Trying pairs...")]
-    [InlineData(NestPhase.Nfp, "Trying NFP...")]
     [InlineData(NestPhase.Extents, "Trying extents...")]
     [InlineData(NestPhase.Custom, "Custom")]
     public void DisplayName_ReturnsDescription(NestPhase phase, string expected)
@@ -18,7 +17,6 @@ public class NestPhaseExtensionsTests
     [InlineData(NestPhase.Linear, "Linear")]
     [InlineData(NestPhase.RectBestFit, "BestFit")]
     [InlineData(NestPhase.Pairs, "Pairs")]
-    [InlineData(NestPhase.Nfp, "NFP")]
     [InlineData(NestPhase.Extents, "Extents")]
     [InlineData(NestPhase.Custom, "Custom")]
     public void ShortName_ReturnsShortLabel(NestPhase phase, string expected)