Fix rules lint/prepare/check failing with "cortex address is required"

[Copilot]

Since v0.18.0, rules lint, rules prepare, and rules check fail with cortex address is required even though these are purely local file operations requiring no Cortex connectivity.

Root cause: The setup PreAction registered on the rules parent command unconditionally validated Address and ID, blocking all subcommands — including local-only ones.

Fix: Split setup into two methods:

• setup (PreAction, runs for all subcommands) — applies config file defaults only, no validation
• setupClient — validates Address/ID and creates the Cortex client; called explicitly only by commands that require Cortex connectivity: list, print, get, delete, delete-namespace, load, diff, sync

# v0.17.0 behavior restored:
$ cortextool rules lint
INFO[0000] SUCCESS: 0 rules found, 0 linted expressions

# Cortex-dependent commands still enforce address:
$ cortextool rules list
cortextool: error: cortex address is required (use --address flag, ...)