Add test_commands_v2.py with 28 tests covering databases, tables,
plugins, schema, default_query, upsert, auth status, actor, and
get commands.
Add test_alias_v2.py with 5 tests for alias default, alias default-db,
and removing the default alias.
Update aliases.md and authentication.md docs for v2 API.
refs #29
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
