Add MITC4 shell NLGEOM finite rotation support

S.Nishiokarequested to merge
SG-Nishioka/FrontISTR:feature/mitc4-shell-nlgeom into master

Closes #762 (closed)

This MR adds finite-rotation nonlinear geometry support for MITC4 shell elements in static analysis.

Main changes:

  • Adds MITC4 shell state variables for Total Lagrangian nonlinear geometry analysis.
  • Updates shell matrix, residual, update, and nodal stress paths for finite-rotation NLGEOM.
  • Adds shell-compatible cutback/state restore handling.
  • Preserves upstream contact, DFORCE, and existing solver paths.

Local verification:

  • Built fistr1 successfully from commit 497ca731.
  • Ran serial CTest: 61/61 tests passed.
  • Confirmed MITC4 shell NLGEOM analysis completed successfully with 10 substeps.

Related issue: #762 (closed)

Related GitHub PR: https://github.com/FrontISTR/FrontISTR/pull/14

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