test(lifecycle): add setup-teardown + run-20x harness scaffolding

Phase 4 of the v1.7.52 container excellence plan: a release-gate harness
that loops the bats suite N times in a row, with teardown between
iterations, and reports a pass/fail tally.

* setup-teardown.sh — clears /tmp/archy-rpc-session-* between runs so
  iteration N+1 doesn't reuse a logged-out cookie from iteration N.
  Idempotent; safe to run anytime. Designed to grow as we add suites
  that leave other transient state.
* run-20x.sh — wraps run.sh in a loop of ARCHY_ITERATIONS (default 20).
  Tracks per-iteration pass/fail with wall-clock timing, prints a
  results block, exits non-zero on any failure. Honors ARCHY_FAIL_FAST
  for short-circuit during dev.

Suggested release-gate command:
  ARCHY_PASSWORD=password123 ARCHY_ALLOW_DESTRUCTIVE=1 \
    tests/lifecycle/run-20x.sh

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/lifecycle/setup-teardown.sh

@@ -0,0 +1,38 @@
+#!/usr/bin/env bash
+# tests/lifecycle/setup-teardown.sh
+#
+# Cleanup helper used between lifecycle test iterations. Run before AND after
+# a full bats pass (run-20x.sh handles this). Idempotent — safe to run any
+# time, on any host.
+#
+# Removes:
+#   - /tmp/archy-rpc-session-* — stale RPC session cookies from earlier runs.
+#     If absent we'd reuse a session that was logged out by an auth.logout
+#     test, then the next iteration would silently 401.
+#   - Per-bats-run scratch files our tests may leave behind (none yet, but
+#     this is the place when we add them).
+#
+# Does NOT touch:
+#   - Real archipelago state (state.json, secrets, packages.json).
+#   - Running containers — destructive container teardown is the test's
+#     responsibility, not the harness's. We only clean the harness's own
+#     transient state.
+#   - SSH known_hosts, archipelago configs, etc.
+
+set -euo pipefail
+
+cleaned=0
+
+# Match the pattern from lib/rpc.bash:26
+session_glob="/tmp/archy-rpc-session-*"
+# shellcheck disable=SC2086 # we want word-splitting on the glob
+for f in $session_glob; do
+  if [[ -f "$f" ]]; then
+    rm -f "$f"
+    cleaned=$((cleaned + 1))
+  fi
+done
+
+if [[ "${ARCHY_TEARDOWN_VERBOSE:-0}" == "1" ]]; then
+  echo "setup-teardown: cleaned $cleaned stale session file(s)"
+fi