[devam007]

Description of Change

Guard empty vectors before constructing the unsigned high index. Handle equal
endpoint values before calculating an interpolation denominator: [7,7,7] with
target 7 previously divided by zero. Preserve the existing return type and
not-found sentinel, and add assertions for empty, singleton and constant inputs.

Validation

GCC 15.2 / C++17: 14,761 reference comparisons pass against std::binary_search
on sorted inputs with duplicates. Found indices are checked to contain the
target without imposing an undocumented first-occurrence requirement. The
constant-input reproduction fails on the base. Warning-enabled compilation with
libstdc++ assertions, the CMake/Ninja target, source assertions and whitespace
checks pass. Remote CI, clang-format and clang-tidy were not run locally.

• Read contribution guidelines and kept the change to one algorithm file
• Added regression assertions and preserved the existing example
• Kept the sorted-input precondition and return contract unchanged