dsh-disk-cleaner: Windows Disk Space Analysis and Safe Cleanup Plugin

`dsh-disk-cleaner` is a Windows disk management plugin under DeepSeek Harness (DSH). It follows the principle of “inspect before you act,” providing a C: drive space overview, intelligent identification and categorization, and cleanup recommendations through a web workspace. Security is its core: it uses deterministic rules and allowlist validation, protects system files by default, requires user confirmation before cleanup, and prefers the Recycle Bin or quarantine area. The deletion feature is currently being tested and refined, aiming to provide developers with a controllable, reversible, and privacy-safe disk cleanup solution.