fix: remove outdated skill file

docs/advanced/acp-http-client.mdx

@@ -1,67 +0,0 @@
----
-title: "ACP HTTP Client"
-description: "Protocol-pure ACP JSON-RPC over streamable HTTP client."
----
-
-`acp-http-client` is a standalone, low-level package for ACP over HTTP (`/v2/rpc`).
-
-Use it when you want strict ACP protocol behavior with no Sandbox-specific metadata or extension adaptation.
-
-## Install
-
-```bash
-npm install acp-http-client
-```
-
-## Usage
-
-```ts
-import { AcpHttpClient } from "acp-http-client";
-
-const client = new AcpHttpClient({
-  baseUrl: "http://127.0.0.1:2468",
-  token: process.env.SANDBOX_TOKEN,
-});
-
-await client.initialize({
-  _meta: {
-    "sandboxagent.dev": {
-      agent: "mock",
-    },
-  },
-});
-
-const session = await client.newSession({
-  cwd: "/",
-  mcpServers: [],
-  _meta: {
-    "sandboxagent.dev": {
-      agent: "mock",
-    },
-  },
-});
-
-const result = await client.prompt({
-  sessionId: session.sessionId,
-  prompt: [{ type: "text", text: "hello" }],
-});
-
-console.log(result.stopReason);
-await client.disconnect();
-```
-
-## Scope
-
-- Implements ACP HTTP transport and connection lifecycle.
-- Supports ACP requests/notifications and session streaming.
-- Does not inject `_meta["sandboxagent.dev"]`.
-- Does not wrap `_sandboxagent/*` extension methods/events.
-
-## Transport Contract
-
-- `POST /v2/rpc` is JSON-only. Send `Content-Type: application/json` and `Accept: application/json`.
-- `GET /v2/rpc` is SSE-only. Send `Accept: text/event-stream`.
-- Keep one active SSE stream per ACP connection id.
-- `x-acp-agent` is removed. Provide agent via `_meta["sandboxagent.dev"].agent` on `initialize` and `session/new`.
-
-If you want Sandbox Agent metadata/extensions and higher-level helpers, use `sandbox-agent` and `SandboxAgentClient` instead.