Replace the static catalog-based model validation with a live API probe.
The /model command now hits the provider's /models endpoint to check if
the requested model actually exists:
- Model found in API → accepted + saved to config
- Model NOT found in API → rejected with 'Error: not a valid model'
and fuzzy-match suggestions from the live model list
- API unreachable → graceful fallback to hardcoded catalog (session-only
for unrecognized models)
- Format errors (empty, spaces, missing '/') still caught instantly
without a network call
The API probe takes ~0.2s for OpenRouter (346 models) and works with any
OpenAI-compatible endpoint (Ollama, vLLM, custom, etc.).
32 tests covering all paths: format checks, API found, API not found,
API unreachable fallback, CLI integration.
- Wrap validate_requested_model in try/except so /model doesn't crash
if validation itself fails (falls back to old accept+save behavior)
- Remove unnecessary sys.path.insert from both test files
- Expand test_model_validation.py: 4 → 23 tests covering normalize_provider,
provider_model_ids, empty/whitespace/spaces rejection, OpenRouter format
validation, custom endpoints, nous provider, provider aliases, unknown
providers, fuzzy suggestions
- Expand test_cli_model_command.py: 2 → 5 tests adding known-model save,
validation crash fallback, and /model with no argument
