Checker recursion depth: valid programs with ~10k-deep terms (e.g. a 10000n literal) fail with "machine stack overflowed"

What you did

# lit.bend
import Base

def main() -> Nat:
  10000n

bend lit.bend (same via the bun/node import hook).

What happened

Error: the machine stack overflowed (a deep recursion, or a literal too large to expand)

• 5000n checks and runs fine; 10000n (and everything larger up to the advertised Number.MAX_SAFE_INTEGER bound) dies.
• The same overflow hits valid non-literal programs: a single def body with ~4,000 sequential do-block statements fails the same way while the same program at 2,000 statements compiles (in 73s — see the separate quadratic-compile report).

So the practical term-depth budget of the checker is ~10k constructor nodes / call frames, well below any documented limit, and the MAX_SAFE_INTEGER guard in parse_term_num (bend.ts:2234) is decorative: nothing between ~10k and 9e15 can ever expand.

The failure itself is handled (caught RangeError with a decent message), so this is a robustness/usability issue, not a crash: valid programs fail with a message that doesn't say which literal or construct was too deep.

Expected

• Make the checker's recursion depth budget explicit and iterative where cheap (the Nat literal expansion loop itself is iterative; the overflow happens downstream in checking/normalization).
• At minimum, catch the overflow at the offending span and report "this literal/term is too large (limit ~N)".

Version / system

• bend 2.0.5 (main @ e6676b0)
• Darwin arm64