feat(shims): expose C path aliases

[Kyle-Ye]

Summary

• Expose a shared path header and ORB aliases for C, C++, and Objective-C clients through OpenRenderBoxShims.
• Select the public headers and backend dependency in the package manifest so clients can use the same API without a backend macro.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 0.00%. Comparing base (ab24fe2) to head (fb5eafe).

Additional details and impacted files

@@          Coverage Diff          @@
##            main     #31   +/-   ##
=====================================
  Coverage   0.00%   0.00%           
=====================================
  Files          8       8           
  Lines        356     356           
=====================================
  Misses       356     356           

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