openspec-agents: Enable agent teams to implement OpenSpec changes following standardized processes.

When working with AI coding tools like DSH, the most common approach is to feed requirements directly into an AI and have it generate the entire codebase from scratch. While this is quick to start, the drawbacks are apparent: the process is opaque, and correctness relies entirely on post-hoc manual inspection; if an error occurs at any step, rolling back is difficult without digging through chat history; and starting a new session breaks the progress. OpenSpec (Fission-AI/OpenSpec, openspec.sh) addresses the first half of this workflow: writing specifications before code, organizing requirements into proposals, designs, tasks, and specs. However, what about after the specifications are written? Implementation, verification, review, and merging still require the user to manually oversee the AI step-by-step. openspec-agents fills precisely this missing gap: