Support configurable provider ID and server-authoritative model metadata

[RaviTharuma]

Problem

For dynamic CLIProxyAPI integration, the plugin currently cannot represent the server catalog and request semantics exactly:

• the provider ID is fixed to cliproxy, rather than configurable (for example, cliproxyapi);
• rich model capabilities/reasoning metadata come from external registries instead of a server-authoritative catalog;
• supported reasoning variants are filtered and omit values such as ultra;
• selected variants do not explicitly propagate the effective reasoning effort in the request payload; and
• catalog failures fabricate built-in fallback models, with no way to require a live-only catalog.

Requested behavior

1. Add a backwards-compatible configurable provider ID, retaining the current default.
2. Accept rich model metadata from the CLIProxyAPI /v1/models response (including effective reasoning variants), treating it as authoritative when present.
3. Preserve all server-advertised reasoning variants, including ultra, and encode the selected effort in outbound requests.
4. Add an option to disable fabricated fallback models so catalog failure can produce an empty/error state instead of invented entries.
5. Keep external mutable enrichment independently disableable.

This would allow exact, auditable live catalogs without relying on mutable third-party registries while preserving existing defaults.