Improve MCC testing workflow resilience

.skills/mcc-integration-testing/scripts/reset_shared_test_state.sh

@@ -0,0 +1,50 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+REPO_ROOT="$(cd "$SCRIPT_DIR/../../.." && pwd)"
+# shellcheck source=tools/mcc-env.sh
+source "$REPO_ROOT/tools/mcc-env.sh"
+# shellcheck source=.skills/mcc-integration-testing/scripts/common.sh
+source "$SCRIPT_DIR/common.sh"
+
+usage() {
+    cat <<'EOF'
+Usage: reset_shared_test_state.sh [--all | <server-dir>...]
+
+Kills shared tmux test sessions and removes stale stdin pipes.
+EOF
+}
+
+if [[ "${1:-}" == "-h" || "${1:-}" == "--help" ]]; then
+    usage
+    exit 0
+fi
+
+kill_named_session() {
+    local session_name="$1"
+    tmux kill-session -t "$session_name" 2>/dev/null || true
+}
+
+kill_named_session "mcc-debug"
+
+if [[ $# -eq 0 || "${1:-}" == "--all" ]]; then
+    while IFS= read -r session_name; do
+        [[ -z "$session_name" ]] && continue
+        kill_named_session "$session_name"
+    done < <(tmux list-sessions 2>/dev/null | awk -F: '/^mc-/{print $1}' || true)
+
+    while IFS= read -r pipe_path; do
+        [[ -z "$pipe_path" ]] && continue
+        if [[ ! -p "$pipe_path" ]]; then
+            rm -f "$pipe_path"
+        fi
+    done < <(find "$MCC_SERVERS" -maxdepth 2 -name 'stdin.pipe' 2>/dev/null || true)
+else
+    for version in "$@"; do
+        kill_named_session "$(server_session_name "$version")"
+        remove_stale_stdin_pipe "$version"
+    done
+fi
+
+rm -f "$MCC_REPO/mcc_input.txt"