dsh-cli-interactive: Interactive Terminal REPL for DeepSeek Harness

The `dsh-cli-interactive` plugin for DeepSeek Harness (DSH) builds a persistent interactive terminal (REPL) on top of the official Profile. It reuses DSH's Agent loop and session persistence capabilities, supporting streaming responses, session history restoration, slash commands, and terminal-based approvals without requiring an additional toolchain. It is well suited for multi-turn code review or debugging. The plugin supports only one session per process, runs in memory, and does not render dynamic effects in pipe mode, making it suitable for long-running interactive scenarios that require continuous availability.