Support using prompt param with GuardrailAgent

[steven10a]

Fixes reported bug from rcatoen:

TypeError: GuardrailAgent.__new__() missing 1 required positional argument: 'instructions' when using prompt instead of instructions

Fix:

• Typing for instruction was too strict required it to be a string
• Functionality was already supported as we are simply a wrapper around Agent SDK

Also added support for users adding their own input and output guardrails via the Agent SDK.

• These were silently suppressed and only guardrails via the config were run
• We now merge the lists and run all of them

Added tests

Some Prettier format changes

[Copilot]

Pull Request Overview

This PR enhances the GuardrailAgent.create() method to support optional instructions (including callable instructions) and allows merging user-provided guardrails with config-based guardrails.

Key changes:

• Made the instructions parameter optional and added support for callable/dynamic instructions
• Added support for merging user-provided input/output guardrails from agentKwargs with config-based guardrails
• Added comprehensive test coverage for the new functionality including edge cases

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/agents.ts	Updated GuardrailAgent.create() to make instructions optional, support callable instructions, and merge user-provided guardrails with config guardrails by extracting them from agentKwargs
src/tests/unit/agents.test.ts	Added extensive test coverage for optional instructions, callable instructions, guardrail merging, and updated MockAgent interface to reflect new signature

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

[nitpick] The Array.isArray() check is redundant since TypeScript already types userInputGuardrails as InputGuardrail[] | undefined. If the value is not an array at runtime, this indicates a type mismatch that should be caught elsewhere. Consider simplifying to just if (userInputGuardrails) for consistency with line 421.

Suggested change

	if (userInputGuardrails && Array.isArray(userInputGuardrails)) {
	if (userInputGuardrails) {

[Copilot]

[nitpick] The Array.isArray() check is redundant since TypeScript already types userOutputGuardrails as OutputGuardrail[] | undefined. If the value is not an array at runtime, this indicates a type mismatch that should be caught elsewhere. Consider simplifying to just if (userOutputGuardrails) for consistency.