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.Engine/NestProgress.cs

@@ -24,9 +24,6 @@ namespace OpenNest
         [Description("Trying pairs..."), ShortName("Pairs")]
         Pairs,
 
-        [Description("Trying NFP..."), ShortName("NFP")]
-        Nfp,
-
         [Description("Trying extents..."), ShortName("Extents")]
         Extents,