fix: prioritize env.vars over channels config to avoid doctor conflicts

fix: use env.vars instead of channels config, channel id remains wecom

refactor: change plugin ID to openclaw-wechat-plugin to match directory

refactor: change plugin ID to openclaw-wechat, remove duplicate manifest

refactor: change plugin ID from wecom to openclaw-wechat

refactor: replace all clawdbot references with openclaw

docs: update proxy port to 3120

feat: OpenClaw WeChat plugin with proxy support