CB-WP-0015: the two inert clauses, AM-7 scaling and AM-8 N=10

Provenance (tier S, one paragraph in lieu of survey and ADR): the two
clauses mutation-check has reported inert since CB-WP-0005. AM-7's
scaling ratio was held up by a test literally named
replay_100k_events_is_linear_and_fast that computed both throughputs,
printed both, and never divided one by the other. AM-8's N=10 was held
up by a runner that does two.

Both are now red. AM-7 3/3, AM-8 2/2, M-D1-MUT 10/14, and ADR-0005's
>=10-of-14 prediction MET for the first time. Neither was closed by
amending the question away, which was the live risk: the denominator is
unchanged and the four unenforced rows are the four already
unenforceable.

AM-7 needed three estimators. Best-of-N per leg then divide (AM-6's,
correct for a floor on one number) gave 0.581-1.085 on an unchanged
binary; legs back-to-back gave medians 0.931-1.004; legs interleaved at
fold granularity give 0.987/0.991/0.989, and 0.989 under 8-way CPU
contention while absolute throughput fell 4x. The INDETERMINATE guard
demanded unanimity and failed a good measurement over one sample
0.001 under the floor; it now requires a two-thirds majority. The
control that matters: AM-6's constant-cost mutation halves throughput
and leaves this ratio at 0.999x green, so AM-7 is not a second AM-6.

AM-8 kept N=10 because the measurement said so. Perturbing the RNG only
from its fourth construction on: --runs 2 PASSES, --runs 10 fails. A
late-onset divergence is deterministic, not flaky, so it is a control
rather than a coin flip. Ten runs live on one scenario (make am8, ~2s)
rather than all 25 (47s a build). GameKernel 5b records it.

The full run also found AM-4a's own mutation stale since ADR-0008 D3
moved the target 250,000 -> 161,000 in CB-WP-0013 -- reported
HARNESS-BROKEN, no score published. The build-free half of that check
is now a --self-test assertion, so make all catches the next one.

mutation-check clauses may now carry their own verify and mutation, and
then the enforced flag is measured rather than declared; a declaration
disagreeing with its measurement is refused.

make all exits 0.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tools/cb-sim/src/main.rs

@@ -17,7 +17,7 @@ const REPLAY_DIR: &str = "replays";
 fn main() {
     let argv: Vec<String> = std::env::args().skip(1).collect();
     if argv.is_empty() {
-        eprintln!("usage: cb-sim <scenario.yaml>...");
+        eprintln!("usage: cb-sim [--runs <n>] <scenario.yaml>...");
         eprintln!("       cb-sim --replay <bundle.cbreplay>...");
         std::process::exit(64);
     }
@@ -28,7 +28,28 @@ fn main() {
     if argv[0] == "--replay" {
         std::process::exit(replay_bundles(&argv[1..]));
     }
-    let args = argv;
+
+    // AM-8 (CB-WP-0015 T02): the replay count. Defaults to K8's two, so
+    // `make sim` is unchanged; `make am8` passes 10 on one scenario.
+    let mut runs = scenario::K8_RUNS;
+    let mut args = argv;
+    if args[0] == "--runs" {
+        if args.len() < 3 {
+            eprintln!("usage: cb-sim --runs <n> <scenario.yaml>...");
+            std::process::exit(64);
+        }
+        runs = match args[1].parse::<usize>() {
+            Ok(n) if n >= 2 => n,
+            // A --runs that silently fell back to 2 would report an
+            // N=10 result after doing an N=2 check — the harness-does-
+            // nothing class this binary's header is about.
+            _ => {
+                eprintln!("--runs needs an integer >= 2, got {:?}", args[1]);
+                std::process::exit(64);
+            }
+        };
+        args = args.split_off(2);
+    }
 
     let mut failed = false;
     let mut passed = 0usize;
@@ -53,7 +74,7 @@ fn main() {
         };
 
         let outcome = match sc.scenario.split('/').next() {
-            Some("ground") => scenario::run::<GroundState>(&sc),
+            Some("ground") => scenario::run_n::<GroundState>(&sc, runs),
             _ => {
                 // A renamed or typo'd prefix would otherwise skip every
                 // scenario while the run still looked clean.