feat(sdk): Add tool definitions from the SDK

[MikeRyanDev]

Summary

• add DirectAgentPayload.tools and exported DirectAgentToolDeclaration types to runtime and SDK surfaces
• validate direct HTTP tool declarations, include them in the OpenAPI request schema, and plumb them into direct-agent prompt processing
• expose these tools to the model as declaration-only prompt tools; execution currently throws a clear unsupported error

Follow-up

• browser/client deferred tool execution and resume semantics are still future work
• this PR only carries caller-scoped tool declarations through the direct-agent request path

Verification

• corepack pnpm --dir packages/runtime run check:types
• corepack pnpm --dir packages/runtime exec vitest run test/direct-agent.test.ts
• corepack pnpm --dir packages/sdk run check:types
• corepack pnpm --dir packages/sdk exec vitest run test/client.test.ts

[astrobot-houston]

Thanks for the contribution! We're closing this PR and moving the conversation to the discussion: #186

We've moved to a model where bugs and feature proposals are discussed in issues/discussions before code review, so the community can help prioritize and shape the work. Your branch is linked from the new thread so the implementation isn't lost — please join us there to continue the conversation.

— astrobot 🤖