feat: profiles can store a test repo (v0.4.8)

[masonlet]

Summary

Profiles can now carry their own test (app) repo, so star-setup --profile NAME
works without repeating the positional repo every time. A CLI input still
overrides the profile's stored test repo.

Changes

• Profile is now a struct ({ test_repo: Option<String>, deps: Vec<String> })
  instead of a bare Vec<String>. Existing .star-setup.json profile entries must be recreated.
• profile add gains --test-repo <user/repo>. A profile is valid with a test repo, dependencies, or both.
• Mono-repo resolution split into three single-purpose steps: find the profile,
  resolve the test repo (cli input to profile), resolve deps (profile to --repos).
• Dropped the old "profile has no repositories" error path, a single-test-repo
  profile is now legitimate.