dsh-compaction-micro: The Micro-Cleanup Layer for DeepSeek Harness

`dsh-compaction-micro` is a standalone plugin for DeepSeek Harness (DSH), designed to quickly free up token space before the official summarization layer by replacing rerunnable tool results on the whitelist with placeholders, thereby avoiding unnecessary and costly model calls. It follows the observer pattern and triggers cleanup only when context pressure exceeds a threshold or an overflow occurs. It supports configuring the cleanup tool whitelist, the number of recent results to retain, and the trigger ratio. After installation, it must be mounted before `dsh-compaction-basic` and applies only to safe, read-only tools.