Fix ctest command in README to point at build/test (Issue #1231)

[lennartvoelz]

enable_testing() is only called in test/CMakeLists.txt, not the top-level CMakeLists.txt, so ctest --test-dir build finds no tests when run from the repo root.

Fixes #1231: Change 'build' to 'build/test'.

With the fix, ctest runs the test suite from the repo root.

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[greptile-apps]

Greptile Summary

Corrects the README test command so CTest runs from the directory where MatX registers its tests.

• Changes ctest --test-dir build to ctest --test-dir build/test.
• Aligns the documented command with the preceding MATX_BUILD_TESTS=ON configuration.

Confidence Score: 5/5

The PR appears safe to merge with no actionable issues identified.

The documented configuration enables the test subdirectory, where CTest is initialized and tests are registered, so build/test is the correct test directory.

Important Files Changed

Filename	Overview
README.md	The updated CTest path matches the test binary directory created by the documented CMake configuration.

_{Reviews (1): Last reviewed commit: "Fix ctest command in README to point at ..." | Re-trigger Greptile}

[cliffburdick]

/build