feat: Add config validation in `NewCacheBackend`

[cryo-zd]

Description / Change would like to make:

NewCacheBackend currently instantiates backends without validating the given CacheConfig, which is error-prone.

semantic-router/src/semantic-router/pkg/cache/cache_factory.go

Lines 10 to 23 in 7a0221b

	// NewCacheBackend creates a cache backend instance from the provided configuration
	func NewCacheBackend(config CacheConfig) (CacheBackend, error) {
	if !config.Enabled {
	// Create a disabled cache backend
	observability.Debugf("Cache disabled - creating disabled in-memory cache backend")
	return NewInMemoryCache(InMemoryCacheOptions{
	Enabled: false,
	}), nil
	}
	switch config.BackendType {
	case InMemoryCacheType, "":
	// Use in-memory cache as the default backend
	observability.Debugf("Creating in-memory cache backend - MaxEntries: %d, TTL: %ds, Threshold: %.3f",

This issue proposes adding a ValidateCacheConfig(Config) call at the start of NewCacheBackend . This ensures invalid configs fail fast and keeps backend creation safe and consistent.

semantic-router/src/semantic-router/pkg/cache/cache_factory.go

Lines 62 to 79 in 7a0221b

	// ValidateCacheConfig validates cache configuration parameters
	func ValidateCacheConfig(config CacheConfig) error {
	if !config.Enabled {
	return nil // Skip validation for disabled cache
	}
	// Check similarity threshold range
	if config.SimilarityThreshold < 0.0 || config.SimilarityThreshold > 1.0 {
	return fmt.Errorf("similarity_threshold must be between 0.0 and 1.0, got: %f", config.SimilarityThreshold)
	}
	// Check TTL value
	if config.TTLSeconds < 0 {
	return fmt.Errorf("ttl_seconds cannot be negative, got: %d", config.TTLSeconds)
	}
	// Check max entries for in-memory cache
	if config.BackendType == InMemoryCacheType || config.BackendType == "" {

Would the team agree with introducing this validation step?

[rootfs]

@cryo-zd do you like to take this up?