Li/differentiable plastic system

[lihanyu97]

Introduce differentiable plasticity solver using staggered solver that updates displacement and internal variables (plastic strain and deformation gradient) seqentially, which mimics the classic plastic return map. The internal variables are represented by DG nodal fields which makes then differentiable through functional. The internal variables are computed via the return map with the latest estimate of displacement. The updated internal variables then feed back to produce the next estimate of the displacement. Convergence is achieved when all residuals evaluated with updated variables are below tolerance.

[Copilot]

🟡 Changes recommended

There are several concrete fixups needed (notably release-notes update plus correctness/maintainability cleanups in the newly added plastic mechanics system and plasticity tests) before this can be safely approved.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR adds a differentiable plasticity capability to Smith’s differentiable-numerics stack and refactors the block-coupling infrastructure so weak forms can depend on the same solved field in multiple argument slots (while keeping history inputs distinct). It also tightens Jacobian API validation and expands test coverage for the new coupling/indexing semantics.

Changes:

• Introduces a new PlasticMechanicsSystem and a differentiable plasticity regression test exercising staggered displacement/internal-variable solves and gradient checks.
• Reworks block indexing from “single slot per (row,col)” to “slot list per (row,col)”, updating FieldStore, SystemSolver, and block_solve accordingly (plus new tests for repeated dependencies and explicit unknown-vs-test fields).
• Adds Jacobian weight-size validation and tests that cover multi-weight Jacobian assembly.

File summaries

File	Description
src/smith/physics/tests/test_functional_weak_form.cpp	Adds a body source and a new test to verify Jacobian-weight linearity across multiple arguments.
src/smith/physics/functional_weak_form.hpp	Adds runtime validation that jacobian_weights.size() matches fields.size().
src/smith/differentiable_numerics/thermal_system.hpp	Updates FieldType construction to match the new FieldType interface (no is_unknown flag).
src/smith/differentiable_numerics/tests/test_porous_heat_sink.cpp	Updates block_solve callsites to the new BlockArgumentMap slot-list format.
src/smith/differentiable_numerics/tests/test_multiphysics_time_integrator.cpp	Adds solver/test utilities and expands tests for repeated dependencies and explicit unknown/test separation; updates naming and assumptions after field-name refactor.
src/smith/differentiable_numerics/tests/test_mixed_poisson.cpp	Updates block_solve callsites to the new BlockArgumentMap slot-list format.
src/smith/differentiable_numerics/tests/test_differentiable_plasticity.cpp	New differentiable plasticity regression tests (primal + internal variables, plus finite-difference gradient checks).
src/smith/differentiable_numerics/tests/CMakeLists.txt	Registers the new differentiable plasticity test in the test build.
src/smith/differentiable_numerics/system_solver.hpp	Updates SystemSolver::solve signature to accept BlockArgumentMap and clarifies docstring meaning.
src/smith/differentiable_numerics/system_solver.cpp	Implements validation and propagation logic using slot lists rather than name-based routing; adds optional staggered-progress logging.
src/smith/differentiable_numerics/system_base.hpp	Clarifies semantics of solve_result_field_names.
src/smith/differentiable_numerics/system_base.cpp	Updates solve/index-map construction and reaction evaluation to use explicit unknown/test field names and slot lists.
src/smith/differentiable_numerics/state_variable_system.hpp	Updates FieldType construction to match the new FieldType interface.
src/smith/differentiable_numerics/solid_mechanics_system.hpp	Updates FieldType construction to match the new FieldType interface.
src/smith/differentiable_numerics/plastic_mechanics_system.hpp	New plastic mechanics system definition and factory, wired for staggered solve of displacement + internal variables.
src/smith/differentiable_numerics/nonlinear_solve.hpp	Introduces BlockArgumentIndices/BlockArgumentMap and updates block_solve signatures/docs.
src/smith/differentiable_numerics/nonlinear_solve.cpp	Implements slot-list driven assembly (inputs, Jacobians, sensitivities) with additional index validation.
src/smith/differentiable_numerics/nonlinear_block_solver.hpp	Adds printLevel() API to support optional staggered-progress logging.
src/smith/differentiable_numerics/multiphysics_time_integrator.cpp	Switches unknown tracking from reaction/test field to explicit solver-owned unknown field name.
src/smith/differentiable_numerics/field_store.hpp	Removes per-FieldType is_unknown flag; introduces explicit {unknown,test} naming, new indexMap() return type, and updated weak-form registration helpers.
src/smith/differentiable_numerics/field_store.cpp	Implements explicit unknown/test name registration and slot-list indexMap() generation with ownership checks.
src/smith/differentiable_numerics/differentiable_test_utils.hpp	Adds optional gradient printout for debugging finite-difference checks.
src/smith/differentiable_numerics/CMakeLists.txt	Installs the new plastic_mechanics_system.hpp header.
.github/workflows/ci-tests.yml	Increases CI build/test job timeout.

Review details

• Files reviewed: 24/24 changed files
• Comments generated: 8
• Review effort level: Lite

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[white238]

so close to what i wanted.. but it does mark it as user facing and you need to do a release notes. I was hoping it would suggest the change to the release notes file. I'll see if i can tweak it .