dsh-push: DeepSeek Harness Lifecycle Push Notification Plugin

`dsh-push` is a DeepSeek Harness (DSH) plugin designed to forward Agent lifecycle events (such as `idle`, `interrupted`, `needInput`, and `exit`) to external channels like Bark, Feishu, and DingTalk for background monitoring and debugging. The plugin is mounted via `cordis.patch.yml`, supports JSON configuration, and provides a rich command-line interface (e.g., viewing status and testing channels). Developers can use `minDurationSec` to filter idle events or `includeSubagents` to include subagent notifications. Note that this plugin does not support message delivery retries, and notifications contain only a lifecycle summary without specific conversation details.