feat(astra): add independent nesting engine and fix hole validation

Replace the Terra scaffold with an independent configuration-space contact placer and bounded stock-plan search. Include plugin tests, synthetic and DXF benchmark drivers, results, and deployment documentation.

Correct shared collision clipping and hole subtraction so curved-hole inserts validate consistently. Cover translated layouts, spacing violations, operand order, winding, and independent boolean-area comparisons.

Validation: 1,293 tests passed with 12 fixture skips; all 34 synthetic/generated and four DXF cases are valid and complete.

OpenNest.Engine.Astra/benchmarks/results/contact-generated.csv

@@ -0,0 +1,24 @@
+case,valid,placed,requested,sheets,area,milliseconds
+generated-library-0-RoundedRectangle,True,24,24,2,1886,175
+generated-library-1-T,True,24,24,2,2016,175
+generated-library-2-Trapezoid,True,24,24,2,2150,120
+generated-library-3-Ngon,True,24,24,2,2024,536
+generated-library-4-Ngon,True,24,24,1,1080,93
+generated-library-5-Ring,True,24,24,1,3901,85
+generated-library-6-PipeFlange,True,12,12,1,966,46
+generated-ring-inserts,True,16,16,2,2016,48
+generated-curved-C,True,16,16,2,2150,1929
+generated-narrow-U,True,24,24,1,3901,136
+generated-stars,True,20,20,1,3901,3118
+generated-seed-00,True,19,19,2,1886,578
+generated-seed-01,True,22,22,2,2016,403
+generated-seed-02,True,21,21,2,2150,1447
+generated-seed-03,True,20,20,1,1012,356
+generated-seed-04,True,24,24,1,1080,600
+generated-seed-05,True,22,22,2,2050,1467
+generated-seed-06,True,27,27,2,1932,1251
+generated-seed-07,True,19,19,1,1032,724
+generated-seed-08,True,17,17,1,1100,980
+generated-seed-09,True,22,22,2,2070,930
+generated-seed-10,True,20,20,1,984,460
+generated-seed-11,True,19,19,1,1050,1151