fix(startup): avoid first-launch config warning

[fcoury-oai]

Why

On a fresh launch, Red loads embedded defaults when config.toml is absent. The default red.log is opened before ~/.config/red exists, however, so startup reports a CFG303 configuration problem and disables logging. Session setup creates the directory later, leaving a misleading warning on the first run.

What

Create the configuration directory at the start of interactive editor startup, before loading runtime configuration. config.toml remains optional; Red still creates the starter file only when the user requests it.

Add a regression test that launches Red with an empty XDG_CONFIG_HOME and checks that the default log opens without creating config.toml.

How to Test

1. Set XDG_CONFIG_HOME to a fresh empty directory and launch the built red in a terminal.
2. Confirm the welcome opens without a configuration-problem warning. Check that red/red.log exists and red/config.toml has not been created unless you choose the starter config.
3. Launch Red again with the same config home and confirm it starts without a configuration warning.

Targeted test: cargo test --test first_launch (passed).