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/dxf/mixed.manifest.json

@@ -0,0 +1,25 @@
+{
+  "sheetSizes": [
+    "120x240",
+    "240x480"
+  ],
+  "spacing": 0.25,
+  "edgeSpacing": 0.5,
+  "parts": [
+    {
+      "dxf": "../../../../OpenNest.Tests/Bending/TestData/4526 A14 PT45.dxf",
+      "quantity": 5,
+      "allowRotation": true
+    },
+    {
+      "dxf": "../../../../OpenNest.Tests/Bending/TestData/4526 A14 PT23.dxf",
+      "quantity": 4,
+      "allowRotation": true
+    },
+    {
+      "dxf": "../../../../OpenNest.Tests/Bending/TestData/4526 A14 PT11.dxf",
+      "quantity": 6,
+      "allowRotation": true
+    }
+  ]
+}