Azure DevOps support for `deps import`

[gosharplite]

I've implemented Azure DevOps support for modelith deps import on a fork branch:

https://github.com/gosharplite/modelith/tree/feat/ado-deps-import

It follows the same "no TLS in modelith" pattern — all network calls go through az rest via the Runner interface. No HTTP client or credential handling in modelith itself.

What's there:

• ParseSource accepts dev.azure.com blob URLs:
  https://dev.azure.com/{org}/{project}/_git/{repo}?path=...&version=GB{branch}
• GB/GT/GC version prefixes mapped to branch/tag/commit in the API calls
• --resource 499b84ac-1321-427f-aa17-267ca6975798 passed to az rest so it gets an AAD token with the correct audience
• Source.Project field added (empty for GitHub)
• ExecRunner.Run shows correct install instructions per CLI (az login vs gh auth login)
• 14 new tests, all CI checks passing

Usage:

az login
modelith deps import \
  "https://dev.azure.com/myorg/myproject/_git/myrepo?path=docs/payments.modelith.yaml&version=GBmain"

I don't have much experience with upstream PRs in open-source world — feel free to reference, adapt, or take anything useful from the branch. If a PR would be helpful I'm happy to open one with some guidance.

The full commit history and an earlier review thread are at gosharplite#1.

p.s. I find modelith extremely useful and use it on my agent tool and several Azure DevOps repos: https://github.com/gosharplite/tell-me-go/tree/main/docs/domain-model#how-modelith-helps-tell-me-go