feat: add Tzafon model provider

[eddieogola]

Summary

• Re-exports tzafon model creator from @inngest/ai, making Tzafon a first-class model provider in AgentKit
• Adds a custom Tzafon adapter for Authorization: Bearer auth that is model-aware about tool calling
• Tool/function calling on Tzafon is model-dependent, so the adapter strips tools/tool_choice only for models that reject them

Files changed

File	Change
packages/agent-kit/src/models.ts	Add tzafon to the re-export from @inngest/ai
packages/agent-kit/src/adapters/tzafon.ts	New adapter — wraps OpenAI parsers, strips tools/tool_choice for sm-* models only
packages/agent-kit/src/adapters/index.ts	Register Tzafon adapter
packages/agent-kit/src/model.ts	Add tzafon format handler (Bearer auth)
docs/src/content/docs/reference/model-tzafon.mdx	Reference page for the Tzafon model
docs/src/content/docs/concepts/models.mdx	Add Tzafon to the models/config/env tabs
docs/astro.config.mjs	Add Tzafon to the reference sidebar

Usage

import { createAgent, createNetwork, tzafon } from "@inngest/agent-kit";

const agent = createAgent({
  name: "assistant",
  system: "You are a helpful assistant.",
  model: tzafon({ model: "tzafon.northstar-cua-fast-1.6" }),
});

Tool calling is model-dependent

Tzafon exposes an OpenAI-compatible chat completions API, but tool/function calling support varies by model (verified against the live API):

• northstar-* models (e.g. tzafon.northstar-cua-fast, tzafon.northstar-cua-fast-1.6) accept tools/tool_choice and emit real tool_calls — they can invoke AgentKit tools.

• sm-* models (e.g. tzafon.sm-1) are deployed without a tool-call parser and reject tools/tool_choice with:

  HTTP 400: "auto" tool choice requires --enable-auto-tool-choice and --tool-call-parser to be set
  

The adapter follows the Grok pattern (wraps the OpenAI parsers with format-specific tweaks) and strips tools/tool_choice only for the sm-* family, passing them through unchanged for models that support them.

Dependency

This PR depends on inngest/inngest-js#1309, which adds the tzafon() model creator and "tzafon" format to @inngest/ai. That PR must be merged and released first, then @inngest/ai should be bumped in packages/agent-kit/package.json before this PR can be merged.

Test plan

• Merge upstream dependency inngest/inngest-js#1309 first
• Bump @inngest/ai to the version containing tzafon
• pnpm build compiles successfully
• pnpm test passes
• Verify tzafon() is importable from @inngest/agent-kit
• Verify sm-* requests strip tools/tool_choice, and northstar-* requests retain them

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🦋 Changeset detected

Latest commit: 65541d6

The changes in this PR will be included in the next version bump.

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Name	Type
@inngest/agent-kit	Minor

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