Improve robustness and documentation of CDHR uniform random walk

[Akash504-ai]

This PR improves the robustness and clarity of the uniform Coordinate Direction Hit-and-Run (CDHR) implementation.

Summary of changes

• Added debug-mode assertions to guard against invalid point dimensions, coordinate indices, and line intersection intervals.
• Documented the stateful nature of the CDHR walk, including its dependence on the previously selected direction and point.
• Clarified assumptions regarding reuse of internal buffers used during line intersection computations.

Notes

• No algorithmic behavior is changed.
• Assertions are active only in debug builds and introduce no overhead in release mode.
• The changes are limited to documentation and safety checks.

Testing

• Built and tested via volesti/test on WSL.
• Multiple test and example targets compiled successfully; the build was terminated late due to resource constraints.
  This addresses the feature request regarding robustness and documentation of CDHR assumptions.
  Closes Improve robustness and documentation of CDHR uniform random walk assumptions #392