Add support for openrouter reasoning + refactor

Started work to make it possible to pass in per-model reasoning config
Cleaned up how we instantiate RequestParameters (TBD: remove
RequestParameters?)

pkg/provider/provider.go

@@ -12,8 +12,61 @@ type Chunk struct {
 	TokenCount       uint
 }
 
+type ModelConfig struct {
+	Provider    string
+	Client      ChatCompletionProvider
+	Model       string
+	MaxTokens   int
+	Temperature float32
+	Reasoning   bool
+}
+
+func NewRequestParameters(modelConfig ModelConfig) RequestParameters {
+	params := RequestParameters{
+		Model:       modelConfig.Model,
+		MaxTokens:   modelConfig.MaxTokens,
+		Temperature: modelConfig.Temperature,
+		Reasoning: ReasoningConfig{
+			Enabled: modelConfig.Reasoning,
+		},
+	}
+	return params
+}
+
+type ReasoningEffort string
+
+const (
+	High   ReasoningEffort = "high"
+	Medium ReasoningEffort = "medium"
+	Low    ReasoningEffort = "low"
+)
+
+// ProviderKind is a bit leaky, it informs the ChatCompletionProvider what
+// provider we're on so we know how to format requests, etc.
+type ProviderKind string
+
+const (
+	OpenRouter ProviderKind = "openrouter"
+	OpenAI     ProviderKind = "openai"
+	Anthropic  ProviderKind = "anthropic"
+)
+
+type ProviderConfig struct {
+	Kind           ProviderKind
+	SupportPrefill bool
+}
+
+type ReasoningConfig struct {
+	Effort    ReasoningEffort
+	MaxTokens int
+	Exclude   bool
+	Enabled   bool
+}
+
 type RequestParameters struct {
-	Model string
+	Provider  ProviderConfig
+	Model     string
+	Reasoning ReasoningConfig
 
 	MaxTokens   int
 	Temperature float32