Remove unsupported optional solver integrations

[astomodynamics]

Summary

This PR removes several unsupported optional solver and neural-dynamics integrations from the repository so the public API, build graph, examples, and tests all reflect the smaller maintained solver surface.

Changes

• remove LibTorch, ACADO, Gurobi, OSQP-backed ASDDP, SQP, SNOPT, ALDDP, and DBAS-DDP integration paths from the top-level CMake build
• drop the related public headers, solver factory registrations, and solver-specific option blocks from the CDDP API
• delete obsolete solver implementations, tests, examples, neural-dynamics training/runtime files, and generated model assets
• update remaining examples that referenced removed solver types to use supported solvers
• trim Docker and README dependency documentation to match the supported build surface
• fix the stray trailing lines in tests/cddp_core/test_boxqp.cpp so the cleaned-up branch still compiles and runs the test suite

Test Plan

• cmake -S . -B /tmp/cddp-cpp-test-build -DCDDP_CPP_BUILD_TESTS=ON
• cmake --build /tmp/cddp-cpp-test-build -j4
• ctest --test-dir /tmp/cddp-cpp-test-build --output-on-failure

Related Issues

• None referenced in this branch.

How to Test

• Check that git diff origin/master...clean_up contains only solver-surface cleanup and related example/test/doc updates.
• Configure and build with the commands listed in Test Plan.
• Run ctest --test-dir /tmp/cddp-cpp-test-build --output-on-failure and confirm the suite reports 100% tests passed.
• Optionally grep for removed integrations, for example rg -n -i "torch|gurobi|osqp|snopt|alddp|dbas_ddp|sqp" from the repo root, to confirm those surfaces are no longer present.

Screenshots/Videos

• None.

Additional Notes

• This branch is intentionally removal-heavy: it deletes unsupported solver families and stale assets rather than replacing them with new functionality.
• Example binaries still build as part of the configured tree, but validation here focused on compile success and the existing automated test suite rather than running each example interactively.

[gemini-code-assist]

Code Review

This pull request removes several solvers (ASDDP, ALDDP, DBAS-DDP) and their associated dependencies (LibTorch, Gurobi, SNOPT) from the project. It also cleans up the CMake configuration, Dockerfile, and documentation to reflect these removals, and updates existing examples to use alternative solvers.