fix(runtime): validate max loop limit

[aiirvizionz]

Summary

• Validate programmatic runScript({ max }) values before creating the loop governor
• Reject zero, negative, and fractional max values with a clear error
• Add regression coverage for invalid max values while keeping existing runtime behavior intact

Why

The CLI validates --max, but direct runScript() callers could pass invalid values. max: 0 stops scripts before any alive loop iteration, while fractional values produce surprising loop counts. The runtime should enforce the same positive-integer contract as the CLI.

Validation

• node --test test\runtime.test.mjs