lua: do-block proper lexical scoping (wrap in (let () …)) +2 tests

lib/lua/test.sh

@@ -902,6 +902,12 @@ cat > "$TMPFILE" << 'EPOCHS'
 (epoch 1705)
 (eval "(lua-eval-ast \"local function f(a, b, ...) return a * 100 + b * 10 + select(\\\"#\\\", ...) end return f(7, 8, 1, 2, 3)\")")
 
+;; ── Phase 7: do-block proper scoping ──────────────────────────
+(epoch 1800)
+(eval "(lua-eval-ast \"local i = 10 do local i = 100 end return i\")")
+(epoch 1801)
+(eval "(lua-eval-ast \"do local i = 10 do local i = 100 assert(i == 100) end assert(i == 10) end return \\\"ok\\\"\")")
+
 EPOCHS
 
 OUTPUT=$(timeout 60 "$SX_SERVER" < "$TMPFILE" 2>/dev/null)
@@ -1358,6 +1364,10 @@ check 1703 "select(2, ...) unpack"          '50'
 check 1704 "sum via ipairs({...})"          '15'
 check 1705 "f(a, b, ...) mixed"             '783'
 
+# ── Phase 7: do-block proper scoping ──────────────────────────
+check 1800 "inner do local shadows"         '10'
+check 1801 "nested do scopes"               '"ok"'
+
 TOTAL=$((PASS + FAIL))
 if [ $FAIL -eq 0 ]; then
   echo "ok $PASS/$TOTAL Lua-on-SX tests passed"