chore: justfile + license maintenance

[adamXbot]

Adds a root justfile per the org convention (recipes delegate to the existing CI/build.sh commands) and adds an MIT LICENSE (holder "Adam Kostarelas", 2026) — the repo previously had no license file.

just --list output:

Available recipes:
    default         # List available commands

    [dev]
    build           # Build the release binary and assemble ClaudeWatch.app (same as CI)
    clean           # Remove build outputs
    run             # Launch the assembled app
    test            # Run the test suite

    [ship]
    release version # Tag v<version> and push it to trigger the sign/notarize/release job

🤖 Generated with Claude Code