dsh-title-index: DeepSeek Harness Web Session Title Index Acceleration Plugin

`dsh-title-index` is a plugin developed for the DeepSeek Harness Web client, designed to address the performance bottleneck caused by the official engine having to decompress large amounts of logs when querying conversation titles. By maintaining a disk-based index cache, it reduces the Top-50 menu title read time from approximately 9.7 seconds to 0.3 seconds. The plugin is implemented by extending and overriding the official engine's `readTitleSnapshots` method, with support for automatic invalidation and re-collapsing, as well as a fallback strategy. Although this feature has now been integrated into the official version and the plugin has been deprecated, it remains in the community directory as a reference implementation.