=== baseline file-rig (audited implementation: ALL PASS) ===
BUILD-OK
rig: kernel strncpy compiled from /usr/src/sys/libkern/strncpy.c
part A (differential vs libc, matrix+fuzz): identical
part B (pad-count: exactly n bytes, canary intact): exact
part C0 src-guard, NUL in window (pad must not read src): no fault (correct)
part C1 src-guard, no NUL, n==window: no fault (reads exactly n)
part D0 dst-guard, n==space: no fault (writes exactly n)
part D1 dst-guard, n==space+1 (caller misuse): SIGSEGV (bound is exactly n)
part D2 src-guard, n==window+1 (caller misuse): SIGSEGV (reads at most n)

ALL PARTS PASS: implementation is libc-identical, reads<=n, writes==n, pad-count exact (0 failures)
rc=0

=== fix build: see fix_build.log ===