Add compatibility test script for third-party Lua projects (issue #24)

Tests lua-TestMore, json.lua, and lume against the Lush binary to verify
parser/lexer/runtime changes don't break standard Lua code.

.gitignore

@@ -13,3 +13,5 @@ testes/libs/all
 
 temp
 lua
+
+compat-tests/

test-compat.sh

@@ -0,0 +1,95 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+LUSH="${LUSH:-$SCRIPT_DIR/lua}"
+COMPAT_DIR="$SCRIPT_DIR/compat-tests"
+
+if [[ "${1:-}" == "--clean" ]]; then
+    rm -rf "$COMPAT_DIR"
+    echo "Cleaned $COMPAT_DIR"
+fi
+
+mkdir -p "$COMPAT_DIR"
+
+# --- Helpers ---
+
+RESULTS_FILE="$COMPAT_DIR/.results.tmp"
+FAIL_COUNT=0
+: > "$RESULTS_FILE"
+
+run_test() {
+    local name="$1"; shift
+    local logfile="$COMPAT_DIR/$name.log"
+    echo "--- Running $name ---"
+    if "$@" >"$logfile" 2>&1; then
+        echo "$name|PASS" >>"$RESULTS_FILE"
+        echo "  PASS"
+    else
+        echo "$name|FAIL" >>"$RESULTS_FILE"
+        echo "  FAIL (see $logfile)"
+        ((FAIL_COUNT++)) || true
+    fi
+}
+
+print_summary() {
+    echo ""
+    echo "=== Compatibility Test Results ==="
+    while IFS='|' read -r name status; do
+        printf "  %-20s %s\n" "$name" "$status"
+    done <"$RESULTS_FILE"
+    echo ""
+    rm -f "$RESULTS_FILE"
+}
+
+clone_or_pull() {
+    local name="$1" url="$2" tag="$3"
+    local dest="$COMPAT_DIR/$name"
+    if [[ -d "$dest" ]]; then
+        echo "--- $name: already cloned ---"
+    else
+        echo "--- Cloning $name @ $tag ---"
+        git clone --depth 1 --branch "$tag" "$url" "$dest"
+    fi
+}
+
+# --- Check Lush binary ---
+
+if [[ ! -x "$LUSH" ]]; then
+    echo "Error: Lush binary not found at $LUSH"
+    echo "Run 'make' first, or set LUSH=/path/to/lua"
+    exit 1
+fi
+
+echo "Using Lush binary: $LUSH"
+echo ""
+
+# === lua-TestMore (TAP test framework) ===
+
+clone_or_pull "lua-TestMore" "https://framagit.org/fperrad/lua-TestMore.git" "0.3.5"
+(
+    cd "$COMPAT_DIR/lua-TestMore"
+    export LUA_PATH="$COMPAT_DIR/lua-TestMore/src/?.lua;;"
+    run_test "lua-TestMore" "$LUSH" test/00require.t
+)
+
+# === json.lua (JSON encoder/decoder) ===
+
+clone_or_pull "json.lua" "https://github.com/rxi/json.lua.git" "v0.1.2"
+(
+    cd "$COMPAT_DIR/json.lua/test"
+    run_test "json.lua" "$LUSH" test.lua
+)
+
+# === lume (utility library, 264 tests) ===
+
+clone_or_pull "lume" "https://github.com/rxi/lume.git" "v2.3.0"
+(
+    cd "$COMPAT_DIR/lume/test"
+    run_test "lume" "$LUSH" test.lua
+)
+
+# === Summary ===
+
+print_summary
+exit "$FAIL_COUNT"