fix: convert last 2 codegen throws to clean error messages

[cs01]

Summary

• The last 2 throw new Error in codegen now produce clean error messages instead of Node.js stack traces
• Users hitting unknown/any parameter types or closure scope errors now see a single-line error message

Changes

• type-system.ts: any/unknown parameter type error → console.error + process.exit(1)
• closure-analyzer.ts: Variable not found in closure scope → console.log + process.exit(1)

Test plan

• All 453 tests pass (node + native)
• Self-hosting Stage 0 + Stage 1 pass
• should reject unknown type in function parameters test still passes