Add instruction / operation counting

[las7]

Problem

Wall-clock timeouts alone do not stop algorithmic blowups.

Proposed change

• Track execution steps or AST operations.
• Terminate execution after a configurable budget.

Acceptance criteria

• Infinite loops terminate deterministically.
• Budget enforced inside interpreter layer.

[las7]

Reviewed. Still valid. Wall-clock/container timeouts exist, but deterministic interpreter-level operation budgets do not. Proposed plan: implement this as part of restricted_python mode using a generated wrapper with a tracing/counting budget for line/op events, configurable per job type, clear timeout/budget-exceeded errors, and tests for infinite loops and algorithmic blowups. Leaving open.