feat: refresh docs and agent schema

docs/index.mdx

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+---
+title: "Overview"
+description: "Universal API for running Claude Code, Codex, OpenCode, and Amp inside sandboxes."
+---
+
+Sandbox Agent SDK is a universal API and daemon for running coding agents inside sandboxes. It standardizes agent sessions, events, and human-in-the-loop workflows across Claude Code, Codex, OpenCode, and Amp.
+
+## At a glance
+
+- Universal HTTP API and TypeScript SDK
+- Runs inside sandboxes with a lightweight Rust daemon
+- Streams events in a shared UniversalEvent schema
+- Supports questions and permission workflows
+- Designed for multi-provider sandbox environments
+
+## Quickstart
+
+Run the daemon locally:
+
+```bash
+sandbox-agent --token "$SANDBOX_TOKEN" --host 127.0.0.1 --port 8787
+```
+
+Send a message:
+
+```bash
+curl -X POST "http://127.0.0.1:8787/v1/sessions/my-session" \
+  -H "Authorization: Bearer $SANDBOX_TOKEN" \
+  -H "Content-Type: application/json" \
+  -d '{"agent":"claude"}'
+
+curl -X POST "http://127.0.0.1:8787/v1/sessions/my-session/messages" \
+  -H "Authorization: Bearer $SANDBOX_TOKEN" \
+  -H "Content-Type: application/json" \
+  -d '{"message":"Explain the repo structure."}'
+```
+
+See the full quickstart in [Quickstart](/quickstart).
+
+## What this project solves
+
+- **Universal Coding Agent API**: standardize tool calls, messages, and events across agents.
+- **Agents in sandboxes**: run a single HTTP daemon inside any sandbox provider.
+- **Agent transcripts**: stream or persist a universal event log in your own storage.
+
+## Project scope
+
+**In scope**
+
+- Agent session orchestration inside a sandbox
+- Streaming events in a universal schema
+- Human-in-the-loop questions and permissions
+- TypeScript SDK and CLI wrappers
+
+**Out of scope**
+
+- Persistent storage of sessions on disk
+- Building custom LLM agents (use Vercel AI SDK for that)
+- Sandbox provider APIs (use provider SDKs or custom glue)
+- Git repo management
+
+## Next steps
+
+- Read the [Architecture](/architecture) overview
+- Review [Agent compatibility](/agent-compatibility)
+- See the [HTTP API](/http-api) and [CLI](/cli)
+- Run the [Frontend demo](/frontend)
+- Use the [TypeScript SDK](/typescript-sdk)