lua: minimal Lua pattern engine for string.find (classes/anchors/quantifiers)

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 — **Lua pattern engine (minimal)** for `string.find`. Supports character classes (`%d`/`%a`/`%s`/`%w`/`%p`/`%l`/`%u`/`%c`/`%x` + complements), `.` any, `^`/`$` anchors, quantifiers `*`/`+`/`-`/`?`, literal chars, `%%`. Added `plain` arg pathway. match/gmatch/gsub still literal. Scoreboard unchanged (pattern-using tests still hit other issues downstream).
 - 2026-04-24: lua: scoreboard iteration — `package.cpath`/`config`/`loaders`/`searchers`/`searchpath` stubs. attrib.lua moves from #9 (checking `package.cpath` is a string) to "module 'C' not found" — test requires filesystem-based module loading, not tractable. Most remaining failures need Lua pattern matching (pm.lua/strings.lua), env tracking (locals.lua/events.lua), or filesystem (attrib.lua).
 - 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.