W14: F8 cross-host differential battery (test-only) — CHECKLIST COMPLETE

Committed replacement for the review's ephemeral 130-probe corpus:
spec/tests/differential-probes.txt (49 probes: F-1 int/float display, K18
overflow, F-3 apply + dict order, S-4 float printing, strings,
collections, special forms, error normalization) evaluated on the native
server (epoch protocol printer) and the SHIPPED WASM kernel
(eval_wasm_probes.js via guest sx-serialize), diffed by
scripts/test-differential.sh with a KNOWN_DIVERGENT heal-detecting ledger.

Result: 46/49 agree. All 3 divergences share one root cause, verified
live: bare sx_server's `apply` does not spread its argument list —
(apply + (list 1 2 3)) errors "Expected number, got list", (apply str l)
returns the serialized list; the WASM kernel spreads correctly and the
test runner masks the bug with its own apply binding (F-7 class).

Finding refinement: F-1's float-display divergence (0.3 vs
0.30000000000000004) is a K.eval JS-boundary artifact — guest-serialized
output agrees across hosts; the battery therefore compares guest
serialization.

This completes the W14 checklist: 7 pin suites, 6 gate scripts/runners,
2 harness capabilities, C9 label cleanup, adapter-dom render coverage.

Test-only: no semantics edits, no push.

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

scripts/test-differential.sh

@@ -0,0 +1,94 @@
+#!/bin/bash
+# test-differential.sh — W14/F8: cross-host differential battery.
+#
+# Evaluates every expression in spec/tests/differential-probes.txt on:
+#   A) the native server (sx_server.exe, epoch protocol) — its printer
+#   B) the SHIPPED browser kernel (eval_wasm_probes.js, guest sx-serialize)
+# and diffs the outputs. The review's original 130-probe corpus was
+# ephemeral (F-8); this is the committed replacement.
+#
+# KNOWN_DIVERGENT is the ledger of confirmed, still-open divergences —
+# keyed by the probe EXPRESSION. Red on a NEW divergence (host drift) and
+# red on a HEALED one (fix landed: delete the entry, locking in parity).
+#
+# Method note (finding refinement, 2026-07-04): comparing raw K.eval
+# JS-boundary values shows float-display divergences (0.3 vs
+# 0.30000000000000004) that DISAPPEAR under guest-level (sx-serialize …) —
+# the F-1 float-display class is a JS-boundary artifact, not a kernel
+# serialization divergence. This battery compares guest serialization.
+set -uo pipefail
+cd "$(dirname "$0")/.."
+
+SERVER=hosts/ocaml/_build/default/bin/sx_server.exe
+WASM=shared/static/wasm/sx_browser.bc.wasm.js
+PROBES=spec/tests/differential-probes.txt
+[[ -x "$SERVER" ]] || { echo "SKIP: $SERVER not built" >&2; exit 2; }
+[[ -f "$WASM" ]] || { echo "SKIP: $WASM missing" >&2; exit 2; }
+
+# --- KNOWN_DIVERGENT ledger (verified live 2026-07-04) -------------------
+# F-3/K53: bare sx_server's `apply` does NOT spread its argument list —
+# (apply + (list 1 2 3)) errors "Expected number, got list"; (apply str l)
+# returns the serialized list as one string. The WASM kernel spreads
+# correctly. The test runner masks this with its own apply (F-7 class).
+declare -A KNOWN_DIVERGENT
+KNOWN_DIVERGENT['(apply + (list 1 2 3))']="F-3: native apply does not spread"
+KNOWN_DIVERGENT['(apply max (list 1 5 2))']="F-3: native apply does not spread"
+KNOWN_DIVERGENT['(apply str (list "a" "b"))']="F-3: native apply does not spread"
+
+native=$(mktemp); wasm=$(mktemp)
+
+python3 - "$SERVER" "$PROBES" > "$native" <<'PY'
+import json, subprocess, sys
+server, probefile = sys.argv[1], sys.argv[2]
+probes = [l.strip() for l in open(probefile) if l.strip() and not l.startswith('#')]
+inp = []
+for i, p in enumerate(probes):
+    inp.append(f"(epoch {i+1})")
+    inp.append(f"(eval {json.dumps(p)})")
+out = subprocess.run(["timeout", "120", server], input="\n".join(inp) + "\n",
+                     capture_output=True, text=True).stdout
+res, cur = {}, None
+for l in out.splitlines():
+    if l.startswith("(ok-len "):
+        cur = int(l.split()[1]); res[cur] = None
+    elif l.startswith("(error "):
+        idx = int(l.split()[1]); res[idx] = "ERROR"; cur = None
+    elif cur is not None and res.get(cur) is None:
+        res[cur] = l; cur = None
+for i, p in enumerate(probes):
+    print(f"PROBE {i+1} {res.get(i+1, '<none>')}")
+PY
+
+timeout 300 node hosts/ocaml/browser/eval_wasm_probes.js "$PROBES" > "$wasm" 2>/dev/null
+
+pass=0; fail=0; i=0
+while IFS= read -r expr; do
+  [[ -z "$expr" || "$expr" == \#* ]] && continue
+  i=$((i+1))
+  a=$(sed -n "s/^PROBE $i //p" "$native")
+  b=$(sed -n "s/^PROBE $i //p" "$wasm")
+  known="${KNOWN_DIVERGENT[$expr]:-}"
+  if [[ "$a" == "$b" ]]; then
+    if [[ -n "$known" ]]; then
+      echo "RED:  $expr — KNOWN_DIVERGENT now AGREES ($known); delete from ledger"
+      fail=$((fail+1))
+    else
+      pass=$((pass+1))
+    fi
+  else
+    if [[ -n "$known" ]]; then
+      echo "KNOWN-DIVERGENT: $expr ($known)"
+      pass=$((pass+1))
+    else
+      echo "RED:  $expr"
+      echo "        native: $a"
+      echo "        wasm:   $b"
+      fail=$((fail+1))
+    fi
+  fi
+done < <(grep -v '^\s*#' "$PROBES" | grep -v '^\s*$')
+
+rm -f "$native" "$wasm"
+echo
+echo "differential: $i probes, $pass in agreement/ledgered, $fail red"
+[[ $fail -eq 0 ]]