Add non-interactive CLI flags, tests, CI, and --version flag

[tomcardoso]

Summary

• Adds --project, --author, --email, --remote, --yes, --help, and --version flags (parsed with the built-in node:util parseArgs — no new dependency) so create-startr can run without a TTY.
• When --project, --author, and --email are all supplied, the interactive prompts are skipped entirely; --yes skips the confirmation step. This is the intended entry point for Claude Code or other coding agents to scaffold a project directly.
• In a non-interactive shell (no TTY): missing required flags now fail fast with a clear error instead of hanging forever on prompts() waiting for stdin that will never arrive. Similarly, the confirmation step refuses to block on input unless --yes is passed.
• Fixes the catch block to call process.exit(1) on failure — previously the process always exited 0 even when scaffolding failed partway through, which breaks any script/agent relying on the exit code to detect success.
• Interactive behavior (no flags passed, TTY attached) is unchanged.
• README updated with a non-interactive usage section.

Added in a follow-up commit:

• Test coverage for all the new CLI paths (--help, --version, missing/partial flags, validation errors, confirmation-refusal) using Node's built-in test runner (node --test, wired to npm test) — no new test-framework dependency.
• A GitHub Actions CI workflow (.github/workflows/ci.yml) that runs the test suite and npm audit --audit-level=high on every push/PR, so dependency vulnerabilities like the simple-git critical RCE fixed in Fix npm audit vulnerabilities #21 get caught automatically going forward.
• An engines: { node: ">=22" } field in package.json, formalizing the Node version requirement the README already documented.

Test plan

• --help / --version print expected output and exit 0
• Non-TTY with no/partial flags → fails fast with a clear "missing required flag(s)" error, exit 1
• Invalid --project/--author/--email values → validation error, exit 1
• All required flags but no --yes in non-TTY → refuses to hang, exit 1 with a clear message
• Full non-interactive run (--project --author --email --yes) → clones, rewrites config.R/README.md, renames .Rproj, removes DESCRIPTION, exits 0 — verified end to end against a real clone
• npm test → 8/8 passing
• npm audit --audit-level=high → 0 vulnerabilities

🤖 Generated with Claude Code