Add support for the Ollama provider in the AI generation pipeline and expose a configurable host address.
New Features:
- Introduce `ollama` as a selectable provider.
- Add `ollama_host` configuration option with default `http://localhost:11434`.
Enhancements:
- Extend provider list in error message to include Ollama.
Enhancements:
- Split ModuleNotFoundError and AttributeError handling to deliver clearer diagnostics
- Explicitly list available providers and flag missing provider classes as packaging bugs
Bug Fixes:
- Provide specific guidance when a provider module is not a built‑in module
- Clarify that a missing provider class indicates a packaging issue rather than user error