dsh-fork-inbox-guard: Drop Inherited Pending Prompts from Forked Sessions

dsh-fork-inbox-guard is a Host plugin designed to address the issue where forking sessions in DeepSeek Harness inherits stale queues, causing new instructions to be deferred. By removing inherited pending prompts, it ensures child sessions prioritize the current input. The plugin can intercept Fork and Branch entry points, logs discarded messages, and remains compatible with the existing Fork algorithm. This tool optimizes the session inheritance process by clearing queues, preventing instruction misalignment.