feat(cli): classify commands and flags as stable/unstable

[h4x3rotab]

Summary

Classify all CLI commands and their flags/arguments as stable or unstable so users know what they can rely on in their scripts.

Motivation

Users need to know which commands and flags are safe to use in automation scripts without risking breaking changes.

Tasks

• Define stability classification criteria (stable, unstable, deprecated)
• Audit all commands and their flags
• Add stability markers to command metadata
• Display stability status in help output
• Document stability policy in README

Commands to classify

• Top-level: status, deploy, login, logout, completion, ssh, cp
• auth: login, logout, status
• cvms: create, list, get, delete, start, stop, restart, upgrade, resize, replicate, attestation
• docker: login, build, push, generate
• nodes: list
• simulator: start, stop, status
• config: list, get, set