CLI polish (Cobra) + config file merge (YAML/JSON + env/flags)

[KingAkeem]

Summary

Adopt Cobra with subcommands and a unified config loader that merges config file, env vars, and flags.

Motivation

• Cleaner UX
• Reproducible runs and easier ops automation

Scope

• Commands: crawl, serve, resume, bench
• --config path; precedence: file < env < flags
• Help text and examples

Acceptance Criteria

• gotor crawl -c gotor.yaml reproduces a run exactly
• --help is clear and complete

Tasks

• Integrate Cobra
• Config loader + precedence rules
• Update README and examples