fix(plugin): default OCP plugin port to 3478 + env-overridable; v3.16.1

ocp-plugin/index.js hard-coded http://127.0.0.1:3456 since the plugin
was created. OCP server moved to 3478 default in v3.14+ as part of
the same wave that renamed the launchd label (dev.ocp.proxy). The
plugin never got the memo. Result: `/ocp usage` from OpenClaw bots
(e.g. the home Telegram bot 大内总管) hit the dead port 3456 and
returned "OCP error: fetch failed".

Fix:
- Default PROXY → http://127.0.0.1:3478
- Read OCP_PROXY_URL env (full URL) first
- Else read CLAUDE_PROXY_PORT env (port only, localhost assumed)
- Else fall back to the 3478 default

openclaw.plugin.json bumped (3.12.0 → 3.16.1) and configSchema
default updated. Plugin version now matches OCP version.

Top-level package.json bumped 3.16.0 → 3.16.1. CHANGELOG entry added.

Diagnostic trail: caught 2026-05-12 when home Telegram bot reported
"OCP error: fetch failed" against `/ocp usage`. Mac mini OCP service
was healthy on port 3478; lsof -iTCP:3456 had no listener; plugin
index.js had hardcoded 3456.

No cli.js citation needed: this is OCP-internal plugin code with no
corresponding cli.js operation.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

ocp-plugin/openclaw.plugin.json

@@ -2,15 +2,15 @@
   "id": "ocp",
   "name": "OCP Commands",
   "description": "Slash commands for the OpenClaw Proxy — /ocp usage, /ocp settings, /ocp health, etc.",
-  "version": "3.12.0",
+  "version": "3.16.1",
   "configSchema": {
     "type": "object",
     "additionalProperties": false,
     "properties": {
       "proxyUrl": {
         "type": "string",
-        "default": "http://127.0.0.1:3456",
-        "description": "URL of the Claude proxy"
+        "default": "http://127.0.0.1:3478",
+        "description": "URL of the Claude proxy. Overridable via OCP_PROXY_URL or CLAUDE_PROXY_PORT env."
       }
     }
   }