dsh-tiered-memory: Tiered Memory and Budget Management Plugin

The DeepSeek Harness (DSH) ecosystem introduces the `dsh-tiered-memory` plugin, addressing issues in the original plugin where user, environment, and project contexts could not be distinguished and memory consumption could not be controlled. Ported from Hermes Agent, it implements tiered storage and budget management. Core features include `mem_set`, `mem_get`, `mem_query` for keyword-routed semantic queries, and `tier_summary` for viewing tier usage and eviction candidates. The architecture divides memory into three tiers with independently managed budgets; when a tier is full, writes are rejected and deletion is prompted. The plugin supports command-based installation, has a high code coverage rate (98.5%) and a strict isolated testing process, and is licensed under MIT.