feat(ai-agents): support custom structured output schemas for AI Agent responses

[asastre]

Description

Allow the AI Agent to return custom structured output message types beyond the built-in ones (text, carousel, etc.). This enables the Flow Builder plugin to instruct the AI Agent to respond with a specific Flow Builder content ID, which is then resolved into its full content with all follow-ups.

Context

Currently, the AI Agent can only return a fixed set of message types. There are scenarios where the AI Agent needs to respond by referencing existing Flow Builder content (e.g. a specific node in the flow) instead of generating a free-form response. This PR makes the output schema extensible so that each consumer can inject its own message types.

Approach taken / Explain the design

1. Generic core interfaces (botonic-core)

• Made BaseMessage, OutputMessage, AgenticOutputMessage, RunResult, and InferenceResponse generic with an Extra type parameter, so they can carry additional message types while remaining backward-compatible (defaults to never).
• Added outputMessagesSchemas to AiAgentArgs to pass extra Zod schemas to the agent.

2. Dynamic output schema (botonic-plugin-ai-agents)

• Extracted base message schemas into a constant array and introduced getOutputSchema(externalSchemas) that merges them with any externally provided Zod schemas at runtime.
• AIAgentBuilder now receives and forwards outputMessagesSchemas.

3. Flow Builder content message (botonic-plugin-flow-builder)

• Created FlowBuilderContentMessage type and its corresponding FlowBuilderContentSchema Zod object, representing a message with a contentId pointing to a Flow Builder node.
• Updated getContentsByAiAgent to:
  • Pass FlowBuilderContentSchema to the AI Agent plugin.
  • Separate the AI Agent response into regular messages and flowBuilderContent messages.
  • Resolve each flowBuilderContent message by fetching the referenced node from the CMS and returning its full contents.

To document / Usage example

To add a custom output message type, define a Zod schema and pass it in outputMessagesSchemas:

const MyCustomSchema = z.object({
  type: z.enum(['myCustomType']),
  someField: z.string(),
})

// When calling the AI Agent plugin
aiAgentArgs.outputMessagesSchemas = [MyCustomSchema]

The AI Agent will then be able to return messages of that type alongside the built-in ones.

As for the new FlowBuilderContentSchema, in the AI Agent prompt you could do something like this:
"If the user is asking for the status of an order, display the Flow Builder content 'OPEN_WISMO_WEBVIEW'"

This will result in the AI Agent returning as a response the contents of the Flow Builder content ID OPEN_WISMO_WEBVIEW directly.

Testing

The pull request has unit tests.

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Test Results

42 tests   42 ✅  1m 21s ⏱️
 5 suites   0 💤
 1 files     0 ❌

Results for commit 88a52ee.