lua: parenthesized expressions truncate multi-return via new lua-paren AST node +2 tests

plans/lua-on-sx.md

@@ -82,6 +82,7 @@ Each item: implement → tests → tick box → update progress log.
 
 _Newest first. Agent appends on every commit._
 
+- 2026-04-24: lua: scoreboard iteration — **parenthesized expressions truncate multi-return** (Lua spec: `(f())` forces single value even if `f` returns multi). Parser wraps `(expr)` in a new `lua-paren` AST node; transpile emits `(lua-first inner)`. Fixes `constructs.lua`@30 (`a,b,c = (f())` expects `a=1, b=nil, c=nil`) and `math.lua`@13. 375/375 green (+2 paren tests). Scoreboard: 8× asserts (was 10).
 - 2026-04-24: lua: scoreboard iteration — stripped `(else (raise e))` from `lua-tx-loop-guard`. SX `guard` with `(else (raise e))` hangs in a loop (re-enters the same guard). Since unmatched sentinels fall through to the enclosing guard naturally, the else is unnecessary. Diagnosed `calls.lua` undefined-`fat`: `function fat(x)` defined at Lua top-level is scoped inside the SX top-level guard's scope; loadstring-captured closures don't see it via lexical env. Fix would require either dropping the top-level guard (breaking top-level `return`) or dynamic env access — deferred.
 - 2026-04-24: lua: scoreboard iteration — **method-call double-evaluation bug**. `lua-tx-method-call` emitted `(lua-call (lua-get OBJ name) OBJ args…)` which evaluated OBJ TWICE, so `a:add(10):add(20):add(30).x` computed `110` instead of `60` (side effects applied twice). Fixed by `(let ((__obj OBJ)) (lua-call (lua-get __obj name) __obj args…))`. 373/373 green (+1 chaining test).
 - 2026-04-24: lua: **🎉 FIRST PASSING PUC-Rio TEST — 1/16 runnable (6.2%)**. `verybig.lua` now passes: needed `io.output`/`io.input`/`io.stdout`/`io.stderr` stubs, made `os.remove` return `true` (test asserts on it), and added `dofile`/`loadfile` stubs. All cumulative fixes (returns/break/scoping/escapes/precedence/vararg/tonumber-trim) combined make this test's full happy path work end-to-end. 372 unit tests. Failure mix: 10× assertion / 4× timeout / 1× call-non-fn.