Fix missing NUL termination for truncated filenames

[atharvmantri]

Terminate truncated Minizip filenames returned by unzGetCurrentFileInfo().

When the ZIP entry filename is at least as long as the caller's output buffer, the existing code reads the full buffer but does not write a terminating NUL. A later unzLocateFile() call can pass that buffer to strlen(), causing an out-of-bounds read. This change reserves one byte for the terminator whenever a nonzero output buffer is supplied and keeps the read length consistent with that reservation.

This addresses #1299.

Validation performed on Windows with native MinGW/CMake:

• cmake --build build-pr1315 --parallel 2 passed, including the Minizip library, CLI targets, and the new regression test.
• CTest passed all 30/30 configured tests, including the new truncated-filename regression and the existing Minizip zip/unzip/compare path tests.
• git diff --check passes.

The regression test links the static Minizip target so it runs without relying on a platform-specific shared-DLL search path. The build directory is local evidence only and is not part of the source change.

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