Support for Multi-Task Execution and Incremental PR Workflow in OpenSpec

[Gopigovind]

Use Case:
Currently, OpenSpec executes changes in a single run. When implementing a feature, it generates more than 50 file changes at once, making it difficult for engineers to review the code effectively.

Requirement:
We need the ability to break down the implementation into multiple smaller tasks based on the requirement. For each task:

Generate corresponding test cases
Implement the changes
Allow engineers to review the changes along with the test cases
Raise a pull request (PR) for that specific task

Once the first task is completed and reviewed, we can proceed to the next task, following the same process.

This incremental approach will improve code review quality, maintainability, and overall development workflow.