Move the CLI application from packages/server/ to apps/cli/ to align
with the monorepo convention (apps/ for deployable applications,
packages/ for shared libraries). Rename package to @openchatlab/chatlab.
Also fix a bug in ensureToken() that used raw string manipulation to
write config.toml, causing duplicate token fields that corrupted the
TOML file. This led to config parse failures and user_data_dir being
overwritten with defaults. Now uses writeConfigField() for safe writes.
