Add alert-channels list, get, and logs commands

[thebiglabasky]

Summary

• Add alert-channels list, alert-channels get, and alert-channels logs to the CLI
• Wire the commands to the public alert-channels and alert-notifications API clients
• Add formatters and focused tests for list, detail, logs, and command metadata
• Register the new alert-channels topic in the CLI package metadata

Testing

• npx tsc -p packages/cli/tsconfig.json --skipLibCheck
• npm run lint
• Focused Vitest coverage for the new alert-channel commands, formatters, and command metadata