Quick-win refactors from the Refactoring Guru catalog:
- Replace Magic Number with Symbolic Constant: extract DEFAULT_TIMEOUT_MS,
DEFAULT_MAX_RETRIES, DEFAULT_MAX_TOKENS, DEFAULT_TEMPERATURE, default
models per provider, and validation prompt into src/constants.ts.
- Parameterize Method: collapse validateTemperature / validateTopP /
validateMaxTokens (and the inline timeout/maxRetries checks) into a
single validateNumberInRange helper with bounds metadata.
- Inline Class / Remove Middle Man: drop the unused ProviderRegistry
class from utils/factory.ts. createProvider now dispatches through
the PROVIDER_REGISTRY const directly instead of a parallel switch.
Also fixes stale VERSION constant in src/index.ts (was 1.3.1).
