litestar: SQLSpecPlugin.get_config() unusable before app registration

[cofin]

Description

SQLSpecPlugin.get_config(name) raises ImproperConfigurationError ("SQLSpec plugin has not been registered with a Litestar application") for both type-based and string-key lookups until on_app_init has run.

The plugin already holds its SQLSpec registry at construction, and that registry knows every registered config, so type/bind-key resolution could be answered without any app-registration state. The registered-app requirement only seems necessary for the DI-key lookups (db_session, db_connection, ...) that are derived during on_app_init.

Use case

Composition roots that build app-scoped adapters/services from the plugin before (or outside) Litestar app construction — e.g. background workers and CLI entry points that share the same wiring. Today the only pre-registration paths are walking plugin.config manually or reaching into the private plugin._sqlspec.

Proposal

• Let get_config(<config type>) and get_config(<bind_key>) resolve from the wrapped registry regardless of registration state, keeping the registered-app requirement only for DI-key string lookups.
• Optionally expose the wrapped registry as a public property (e.g. plugin.sqlspec) so integrators don't need _sqlspec.

Version

sqlspec 0.58.x (litestar extension)