Pull requests on Azure Repos

trau now delivers to Azure Repos: it opens pull requests, waits on branch policies, and answers review feedback. Azure Boards comments keep their formatting.

Added

A repository hosted on Azure Repos gets pull requests, policy-driven merges and review feedback, so Azure DevOps teams can run the full loop
Review votes, comment threads, replies and resolved threads on an Azure Repos pull request steer the run the way they do on other forges
Onboarding asks for the Azure DevOps token when a repository delivers to Azure Repos, and reads the base branch's build policies as the merge gate
trau doctor checks that the Azure DevOps token reaches each repository and that the Azure Boards project exists

Fixed

Azure Boards comments keep their tables, code blocks and screenshots instead of arriving as plain text
Removing a label or a tag on an Azure Boards work item now takes effect instead of leaving the old tag in place