dsh-insight-tree: DSH Runtime Observability and Plugin Diagnostics

`dsh-insight-tree` is a runtime observability and plugin diagnostics panel for DeepSeek Harness (DSH). It aggregates profile configurations, installation packages, loader status, session activity, and version information to generate visual reports. Its core features include comprehensive diagnostics, plugin management (with support for disabling, reloading, and uninstalling), standalone diagnostic tools, and startup failure attribution. This tool helps developers troubleshoot issues through a plugin tree and command-line interface, includes compatibility checks and dry-run protection, and supports offline standalone diagnostics.