CLI now reads `[shared].registry_url` and `[cli].cookie` from the unified
file via maestro-config instead of `~/.config/maestro/cli.toml`. The
two persistence paths are now distinct:
- `maestro set-registry <url>` → writes `[shared].registry_url`
- captured Set-Cookie on first contact → writes `[cli].cookie`
Both go through read-modify-write so they preserve any `[daemon]` /
`[registry]` content already in the file.
Env-var renames on the CLI flag layer:
- `--registry-url` reads `MAESTRO_SHARED_REGISTRY_URL` (was `MAESTRO_REGISTRY_URL`)
- `--config` reads `MAESTRO_CONFIG` (was `MAESTRO_CLI_CONFIG`)
Default config path is now `~/.config/maestro/config.toml`.