fix(code-runtime): validate arguments before worker dispatch

packages/code-runtime/code-runtime-worker/tests/output-json.spec.ts

@@ -0,0 +1,18 @@
+import { describe, expect, it } from 'vitest'
+import { truncateJsonStringBytes } from '../src/output-json.ts'
+
+describe('truncateJsonStringBytes', () => {
+  it('returns a fitting string whole and rejects budgets without JSON quotes', () => {
+    expect(truncateJsonStringBytes('fits', 6)).toBe('fits')
+    expect(truncateJsonStringBytes('x', 1)).toBe('')
+  })
+
+  it('accounts every JSON escape and cuts only between complete code points', () => {
+    const prefix = '"\\\b\t\n\f\r\u0000😀\ud800€a'
+    const text = `${prefix}z`
+    const budget = Buffer.byteLength(JSON.stringify(prefix), 'utf8')
+
+    expect(truncateJsonStringBytes(text, budget)).toBe(prefix)
+    expect(Buffer.byteLength(JSON.stringify(truncateJsonStringBytes(text, budget)), 'utf8')).toBe(budget)
+  })
+})