FESADev/phases/property-model-foundation/step2.md

Step 2: shell-property-polymorphism

Read First

Read these files before editing:

• /AGENTS.md
• /docs/AGENT_RULES.md
• /docs/implementation-plans/property-model-foundation-implementation-plan.md
• /include/fesa/property/Property.hpp
• /include/fesa/property/ShellProperty.hpp
• /src/property/ShellProperty.cpp
• /tests/property/shell_property_test.cpp

Task

Make ShellProperty derive from Property.

Required behavior:

• ShellProperty::id() overrides Property::id().
• ShellProperty::kind() returns PropertyKind::Shell.
• ShellProperty keeps materialId() and thickness() accessors.
• Constructor still rejects thickness <= 0.0.

Rules:

• Do not rename ShellProperty in this phase.
• Do not add shell section stiffness.
• Do not add material lookup inside ShellProperty; Domain validates cross references.

Tests To Write First

• Extend /tests/property/shell_property_test.cpp.
• Test const Property& base = shell_property exposes id and kind.
• Preserve positive-thickness validation tests.

Acceptance Criteria

ctest --test-dir build/msvc-debug --output-on-failure -C Debug -R model-object
python scripts/validate_workspace.py

Verification Notes

1. Run targeted CTest before production edits and confirm failure.
2. Keep ShellProperty free of solver state.
3. Update phases/property-model-foundation/index.json for this step result.