Documentation

This migration converts the codebase from having all projects in a single codebase root to having separate causal roots for each project branch. It:

• Adds the new project reflog table
• Adds the project-branch head as a causal-hash-id column on the project-branch table, and populates it from all the projects in the project root.
• Makes a new legacy project from the existing root branch (minus .__projects)
• Adds a new scratch/main project
• Adds a currentProjectPath table to replace the most-recent-path functionality.

It requires a Connection argument rather than working inside a Transaction because it needs to temporarily disable foreign key checking, and the foreign_key pragma cannot be set within a transaction.