24. The Plain Call Path in the Iterative VM

• The iterative VM sent every rule call, memoized or not, through callBegin and callEnd (examined-range bookkeeping, state copies) and through the full invokeBegin / invokeEnd. Its call frame now takes the same paths as parser.call: unmemoized calls of rules without captures run the steps of invokePlain, other unmemoized calls skip the memo bookkeeping, and only memoized calls use callBegin and callEnd.
• callBegin used to decide again whether to memoize, so the recursive backends called firstCall twice for each memoized call and counted every repeat twice (change 18). The caller now decides once. The threshold for eager memoization went from 8 to 16 so that rules switch as before (minilang allocates the same as before).
• Effect (min of 6 interleaved runs, Apple M3 Max), iterative VM: full parses JSON 33.2 → 26.0 ms, XML 31.6 → 25.5 ms, Arith_OperatorsRule 24.1 → 21.7 ms, Arith_LeftRec 44.7 → 39.8 ms, minilang 30.7 → 28.2 ms; recognition JSON 28.5 → 20.3 ms, XML 29.7 → 23.2 ms. Other backends unchanged.