DeepSeek Harness Session Context Menu Plugin

The `dsh-session-context-menu` plugin provides Codex-style context operations for DeepSeek Harness session management without patching packages or querying private DOM. It supports pinning, marking as read, copying messages, and integrated actions such as renaming and archiving, invocable via right-click or keyboard shortcuts. State is stored only in a local JSON file and does not involve sensitive data, though it requires DSH to provide specific interface support.