Tag 3-5 issues as 'good first issue' for new contributors

[skokaina]

Why

After the launch post, there's a burst of potential contributors who check the Issues tab. If nothing is approachable, they leave. 3-5 well-scoped "good first issue" items convert browsers into contributors.

Candidate issues to tag

Pick from or create small, self-contained tasks like:

1. Add IDE autocomplete setup to docs — document how to configure VS Code YAML extension with `schemas/v1/agent.schema.json` (~5 lines of docs)
2. Add `.env.example` to `examples/gymcoach/` — list all required env vars with placeholder values
3. Add `--verbose` flag to `agentspec init` — show a summary of chosen values before writing the file
4. Add `agentspec doctor` command — print Node version, npm version, installed packages (diagnostic info for bug reports)
5. Improve CLI error message when agent.yaml not found — currently throws a generic YAML parse error; should say "agent.yaml not found in current directory"

Acceptance criteria

• At least 3 issues tagged `good first issue` before launch
• Each has clear scope, expected output, and file paths
• Mix of code and docs tasks (lower barrier for first contribution)