dsh-branch-inbox-guard: Resolving Queue Contamination Caused by DSH Branches Inheriting Parent Queues

This plugin is designed to resolve an issue in DeepSeek Harness (DSH) 0.1.5 where forked sub-sessions inherit the parent session's unprocessed queue, causing new input to be blocked. Implemented as a host-side Bundle, it automatically removes inherited queue items inserted before the fork point (`seq < session.inheritedEventCount`) when the `agent/created` event fires, ensuring that the newly created branch prioritizes processing user input. The installation is simple and requires no configuration. Compatibility with DSH 0.1.5 and earlier versions has been verified.