Build fails on macOS/clang: MAX_LINES treated as VLA triggers -Wgnu-folding-constant

[dbarabashh]

Env: macOS (clang via Xcode CLT), current master, make with repo defaults.

clang errors in src/runna.c:
src/runna.c:41:12: error: variable length array folded to constant array as an extension [-Werror,-Wgnu-folding-constant]
char path[MAX_LINES];
This happens because MAX_LINES is a const int, which is not a compile-time constant for array bounds in C under clang, so it’s treated as a

VLA and the GNU extension is an error under -Werror.
Fix: make MAX_LINES a real compile-time constant, e.g. #define MAX_LINES 500 (or enum { MAX_LINES = 500 };). This resolves the clang warning/error and make succeeds.