[petlenz]

What

• core/stress_like.h: stress_like<T> is a tmech::tensor<T, 3, 2> that marks a history property as stress-like. It inherits the tensor's constructors and assignment, and an is_tensor_type specialization lets it take part in tmech expressions.
• A material declares the kind with the type: add_history_output<stress_like<value_type>>("back_stress").
• statev_map stores it with stress_to_buffer / stress_from_buffer, so the host sees σ₁₂ rather than 2σ₁₂. Plain tensor2 history keeps the strain convention (default, unchanged), and describe() marks the entry [stress].

No files of the open PRs are touched (material_base.h and property_traits stay as they are); the kinematic-hardening model of #20/#55 can use the type for its back stress.

Tests

StatevMap.StressLikeHistoryKeepsItsShearComponentsForTheHost in test_material_point_evaluator.cpp, using a probe material with a stress-like and a strain-like history. It checks:

• the host slot σ₁₂ = 0.1 next to γ₁₂ = 0.2;
• the round trip of both;
• the [stress] marker.

It failed to compile before (no stress_like). GCC 14 Debug with fetched dependencies: 622/622.

Closes #63

[petlenz]

Review findings (design, tmech expressions instead of component loops, modern C++, comments, tests, correctness). Severity: must = wrong result, hang, build break or unreachable feature; should = design, duplication, accuracy; nit = style.

STATEV stress-like — needs changes

• [must] statev_map.h:249-286 hist_stress2 is a verbatim copy of hist_tensor2 → one add_tensor2_entry<bool ShearStrain> using tmech::abq_std<3, ShearStrain> (exactly how tensor_conversion.h:180/197 distinguishes them).
• [must] file docblock :40-44 still says tensor history is strain-like globally.
• [should] unsupported-type message omits stress_like; stress_like<T, Dim> has a Dim that statev cannot honour; test lives in the evaluator test file instead of test_statev_map.cpp; stress_like by inheritance bypasses tmech's exact-type array copy (note it, or use a trait).
• [nit] nested ternary at :169.

Conflicts and landing order (open PRs on main)

• tests/CMakeLists.txt: core: reject malformed models instead of running them (#56, #57, #60, #64, #69) #79 and core: fail loudly when a material reaches for something unwired (#59, #62) #84 both insert after test_property_graph; solvers: report a Runge-Kutta step that did not converge (#58, #61) #83 vs main's foreach; tests: drive vector_newton through a real return map (kinematic hardening) #55 vs main.
• core/material_interface.h: core: fail loudly when a material reaches for something unwired (#59, #62) #84 and io: name the parameter, the material and the entry when a deck is wrong (#66, #67) #85 overlap.
• Order: core: fail loudly when a material reaches for something unwired (#59, #62) #84 → io: name the parameter, the material and the entry when a deck is wrong (#66, #67) #85 (rebased on it) → core: reject malformed models instead of running them (#56, #57, #60, #64, #69) #79 → solvers: report a Runge-Kutta step that did not converge (#58, #61) #83; solvers: drop the relative-residual guard, it fired on rounding noise (#21) #53 merges clean; tests: drive vector_newton through a real return map (kinematic hardening) #55/cmake: make the installed package compile for a consumer (#70, #71) #81/build: clean the warning set and enforce it in CI (#76) #86 rebase onto 7bcba93 and shrink to their non-CMake content.
• STATEV: stress-like tensor history without the engineering-shear factor (#63) #91 ↔ tests: drive vector_newton through a real return map (kinematic hardening) #55: back_stress becomes stress_like.