lua: do-block proper lexical scoping (wrap in (let () …)) +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 — **`do`-block proper scoping**. Was transpiling `do ... end` to a raw `lua-tx` pass-through, so `define`s inside leaked to the enclosing scope (`do local i = 100 end` overwrote outer `i`). Now wraps in `(let () body)` for proper lexical isolation. 355 tests, +2 scoping tests.
 - 2026-04-24: lua: scoreboard iteration — `lua-to-number` trims whitespace before `parse-number` (Lua coerces `" 3e0 "` in arithmetic). math.lua moved past the arith-type error to deeper assertion-land. 12× asserts / 3× timeouts / 1× call-non-fn.
 - 2026-04-24: lua: scoreboard iteration — `table.getn`/`setn`/`foreach`/`foreachi` (Lua 5.0-era), `string.reverse`. `sort.lua` unblocked past `getn`-undef; now times out on the 30k-element sort body (insertion sort too slow). 13 fail / 3 timeout / 0 pass.
 - 2026-04-24: lua: scoreboard iteration — parser consumes trailing `;` after `return`; added `collectgarbage`/`setfenv`/`getfenv`/`T` stubs. All parse errors and undefined-symbol failures eliminated — every runnable test now executes deep into the script. Failure mix: **11× assertion failed**, 2× timeout, 2× call-non-fn, 1× arith. Still 0/16 pass but the remaining work is substantive (stdlib fidelity vs the exact PUC-Rio assertions).