ci: the dict_hash check counts three hashes, not one distinct value (#172)

The stick-high stage passed when one distinct dict_hash appeared: an
architecture whose boot left no accept file, no LOG: line, no serial log or no
PARITY:V4_SYSTEM line gave nothing, and two that agreed passed for three.

It is now a stage of its own, scripts/nightly.sh dict-hash, which stick-high
runs: one hash from each of amd64, aarch64 and riscv64, all found and one value;
otherwise refused, naming the architectures with none or the values that
differ. NIGHTLY_OUT points the stages at another directory, for the tests.

scripts/test_nightly_dict_hash.sh, written first and seen to fail (6 of 6, the
stage not existing), then 7 cases: agree -- pass; differ, no PARITY line, no
LOG: line, not booted, no serial log, none at all -- refused. Two of them
caught lookups that ended the script silently under set -e; guarded.

Captain Bob, 2026-11-12: "172 then finish alpha.5".

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017RzZgrf7V7Zk2iczBXDRbm

scripts/test_nightly_dict_hash.sh

@@ -0,0 +1,62 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: LicenseRef-Starship-1.0
+# Copyright (c) 2023-2026 Robert A. James
+# test_nightly_dict_hash.sh -- the tests of `scripts/nightly.sh dict-hash` (#172): the three
+# architectures' boots agree on one dict_hash only when all three report one, and it is the same.
+# No QEMU: each case is a scratch NIGHTLY_OUT with accept-<arch>.txt files and serial logs, as the
+# accept stages leave them.
+#
+# Prints PASS:/FAIL: per check and RESULT:; exits 0 only if every check passes.
+set -uo pipefail
+NIGHTLY="$(cd "$(dirname "$0")" && pwd)/nightly.sh"
+T=$(mktemp -d)
+trap 'rm -rf "$T"' EXIT
+ok=1
+
+boot() {  # boot <arch> <hash|none|nolog|nofile>: what accept <arch> leaves
+    local a=$1 h=$2 log="$T/logs/$1.log"
+    mkdir -p "$T/out" "$T/logs"
+    case $h in
+        nofile) rm -f "$T/out/accept-$a.txt"; return ;;
+        nolog)  printf 'RESULT: PASS\n' > "$T/out/accept-$a.txt"; return ;;
+    esac
+    printf 'LOG: %s\nRESULT: PASS\n' "$log" > "$T/out/accept-$a.txt"
+    if [ "$h" = none ]; then printf 'POST: PASSED\n' > "$log"
+    else printf 'PARITY:V4_SYSTEM word_count=318 dict_hash=%s\nPOST: PASSED\n' "$h" > "$log"; fi
+}
+
+expect() {  # expect <pass|refuse> "what"
+    local want=$1 what=$2 out rc
+    out=$(NIGHTLY_OUT="$T/out" bash "$NIGHTLY" dict-hash 2>&1); rc=$?
+    if { [ "$want" = pass ] && [ $rc -eq 0 ]; } ||
+       { [ "$want" = refuse ] && [ $rc -eq 1 ] && grep -q "do not agree" <<<"$out"; }; then
+        echo "PASS: $what"
+    else
+        echo "FAIL: $what (exit $rc)"; printf '      %s\n' "$out" | head -4; ok=0
+    fi
+}
+
+H=0x8c92508f748f99cf
+boot amd64 $H; boot aarch64 $H; boot riscv64 $H
+expect pass   "three boots, one dict_hash: pass"
+
+boot riscv64 0x0000000000000001
+expect refuse "two hashes differ: refused"
+
+boot riscv64 none
+expect refuse "one log has no PARITY:V4_SYSTEM line (two agree): refused"
+
+boot riscv64 nolog
+expect refuse "one accept-<arch>.txt names no LOG: (two agree): refused"
+
+boot riscv64 nofile
+expect refuse "one architecture was not booted (two agree): refused"
+
+boot riscv64 $H; rm -f "$T/logs/riscv64.log"
+expect refuse "one serial log is missing (two agree): refused"
+
+rm -f "$T/out/accept-"*.txt
+expect refuse "no architecture booted at all: refused, and says so"
+
+echo "RESULT: $([ $ok = 1 ] && echo PASS || echo FAIL)"
+[ $ok = 1 ]