feat: add property model foundation

phases/property-model-foundation/index.json

@@ -0,0 +1,36 @@
+{
+  "project": "FESA Structural Solver",
+  "phase": "property-model-foundation",
+  "steps": [
+    {
+      "step": 0,
+      "name": "property-base-contract",
+      "status": "completed",
+      "summary": "Created the property model foundation implementation plan with runtime Property ownership rules and HDF5 skeleton limits."
+    },
+    {
+      "step": 1,
+      "name": "property-base-interface",
+      "status": "completed",
+      "summary": "Added PropertyKind and abstract Property base with polymorphic ownership tests."
+    },
+    {
+      "step": 2,
+      "name": "shell-property-polymorphism",
+      "status": "completed",
+      "summary": "Made ShellProperty derive from Property while preserving material id and positive-thickness validation."
+    },
+    {
+      "step": 3,
+      "name": "domain-property-ownership",
+      "status": "completed",
+      "summary": "Migrated Domain property storage to std::unique_ptr<Property> with shell-property compatibility accessors and cross-reference validation."
+    },
+    {
+      "step": 4,
+      "name": "validation-report-handoff",
+      "status": "completed",
+      "summary": "Validated targeted CTest, workspace validation, script self-tests, and whitespace checks; updated project progress."
+    }
+  ]
+}