33. Smaller VM Entries

• Every choice and every repetition iteration pushes an entry onto the VM's entry stack. Entries were 112 bytes, mostly fields that only @error labels, #recover and skip entries use; in profiles, pushing them was the most expensive line of the VM loop. Those fields moved to a separate stack (vmMachine.labs, indexed from the entry), and the stack heights in the saved state are int32: an entry is now 56 bytes.
• Effect (min of 6 interleaved runs, Apple M3 Max): both VMs 1–5% faster on full parses (JSON bytecode 18.8 → 18.0 ms, XML 19.0 → 18.2 ms) and 2–6% on recognition, including the error-recovery workload.