dsh-plugin-project-management: Generate project timeline in DSH and export to Word/Excel

`dsh-plugin-project-management` is a project management plugin based on DeepSeek Harness (DSH), designed to integrate project interviews, timeline generation, task scheduling, and document export into a unified workflow. The plugin collects project information via the `project-interview` skill, utilizes a deterministic scheduling engine to generate workday-aware Gantt charts that support dependencies, and allows for task adjustments. Key features include project definition validation and persistence, cross-session state recovery, and exporting results in Word (.docx) or Excel (.xlsx) formats. State data is stored in the `project_data.json` file within the workspace, supporting project management across multiple sessions. The plugin provides a Web UI interface.