ACP: revert acpx-plugin package naming (#52456)

* ACP: revert acpx-plugin package naming

* Test: format acp install hints expectations

extensions/acpx/package.json

@@ -1,5 +1,5 @@
 {
-  "name": "@openclaw/acpx-plugin",
+  "name": "@openclaw/acpx",
   "version": "2026.3.22",
   "description": "OpenClaw ACP runtime backend via acpx",
   "type": "module",

extensions/acpx/skills/acp-router/SKILL.md

@@ -109,7 +109,7 @@ Do not default to subagent runtime for these requests.
 
 ## ACPX install and version policy (direct acpx path)
 
-For this repo, direct `acpx` calls must follow the same pinned policy as the `@openclaw/acpx-plugin` extension package.
+For this repo, direct `acpx` calls must follow the same pinned policy as the `@openclaw/acpx` extension package.
 
 1. Prefer plugin-local binary, not global PATH:
    - `./extensions/acpx/node_modules/.bin/acpx`