feat: multi repo profiles (v0.6.0)

[masonlet]

Summary

Lets a profile define multiple test repos (e.g. several games sharing one library set) and builds/runs them together in a single mono-repo invocation.

Changes

• Profile is now { test_repos: BTreeMap<String,String>, deps: BTreeMap<String, Vec> }: multiple keyed test repos and dependency sets, replacing the single test_repo / flat deps. BTreeMap keeps clone/build/script output deterministic across runs. Missing fields default via #[serde(default)].
• profile add takes --test-repos a b … and --deps a b … (replaces --test-repo + bare positional). Positional repo and --profile are now mutually exclusive (conflicts_with).
• Mono mode resolves every test repo on a profile, clones/builds them into one workspace, and generates a dev server entry per repo. Setup header and completion summary show a count by default, full list under --verbose.
• Watch and dev now share one script generator; both emit .ps1/.sh that launch each entry in its own terminal. dev.ps1/dev.sh are generated by default.
• README updated for the new flags, multi-repo profiles, the stored JSON shape, and dev-script generation.