== Part 1: kernel index/rindex vs libc strchr/strrchr ==
  MISMATCH baseline str[0]="" ch=-256 kernel=-1 libc=0
  MISMATCH baseline str[0]="" ch=-256 kernel=-1 libc=0
  MISMATCH baseline str[0]="" ch= 256 kernel=-1 libc=0
  MISMATCH baseline str[0]="" ch= 256 kernel=-1 libc=0
  MISMATCH baseline str[1]="a" ch=-256 kernel=-1 libc=1
  MISMATCH baseline str[1]="a" ch=-256 kernel=-1 libc=1
  MISMATCH baseline str[1]="a" ch=-159 kernel=-1 libc=0
  MISMATCH baseline str[1]="a" ch=-159 kernel=-1 libc=0
  MISMATCH baseline str[1]="a" ch= 256 kernel=-1 libc=1
  MISMATCH baseline str[1]="a" ch= 256 kernel=-1 libc=1
  MISMATCH baseline str[2]="abc" ch=-256 kernel=-1 libc=3
  MISMATCH baseline str[2]="abc" ch=-256 kernel=-1 libc=3
DIFF baseline: index    58 mismatches, rindex    58 mismatches
BASELINE_TOTAL_MISMATCHES=116
== Part 2: ch==0 semantics (strchr/strrchr NUL tail) ==
CH0_SEMANTICS: OK — match libc exactly (0 bad)
== Part 3: guard-page (pagesize=4096) ==
guard k_index '/'    -> off 6  [no fault]
guard k_rindex 'z'   -> off 8  [no fault]
guard k_index 0      -> off 9 (want 9) [no fault]
guard k_rindex 0     -> off 9 (want 9) [no fault]
guard k_index 'Q'    -> NULL [no fault]
guard NONUL k_index  -> FAULT at guard page (contract demo, expected)
GUARDPAGE_RESULT: byte-exact, halts at NUL (0 unexpected faults)
== Part 4: patched (*u.p == (char)ch) differential ==
DIFF patched: index     0 mismatches, rindex     0 mismatches
PATCHED_TOTAL_MISMATCHES=0
HARNESS_DONE