v0.4.0

Breaking change release - renames the Homebrew package from
`mainwp` to `mainwp-cli`, and the config directory from
`/.config/mainwp/` to `/.config/mainwp-cli/`. The CLI
binary name (`mainwp`) is unchanged, so `mainwp sites list`,
`mainwp --version`, `mainwp config`, etc. all keep working
exactly as before.

Migration

Existing users need to do:

```bash
brew uninstall mainwp
brew install mainwp-cli

re-create the profile (the old config is not read)

mainwp init
```

If you have multiple profiles, you can copy the old config
into the new location instead of re-creating it from scratch:

```bash
mkdir -p ~/.config/mainwp-cli
cp ~/.config/mainwp/config.json ~/.config/mainwp-cli/config.json
chmod 600 ~/.config/mainwp-cli/config.json
```

Why a clean cut

A fallback path that read the old `/.config/mainwp/` and
wrote the new `/.config/mainwp-cli/` was considered and
explicitly rejected: the per-profile permission setup, the
chmod 600 contract, and any backups all need to follow the same
root. A dual-path setup would have ambiguous behavior the first
time the user runs `mainwp init`.

What is unchanged

• The CLI binary on `$PATH` is still `mainwp`. All commands,
  flags, profiles, and env-var overrides work as in 0.3.6.
• All 61 smoke tests pass.
• The skill bundle (skills/mainwp-cli/SKILL.md) has been
  updated to mention `brew install mainwp-cli`.

```
brew install mainwp-cli
mainwp --version
mainwp 0.4.0
```