providers: finalize PR213 review fixes

Phase 1: centralize protocol message/tool/response types in protocoltypes and keep compatibility aliases in providers and protocol packages.

Phase 1: preserve HTTPProvider constructor compatibility and route Anthropic api_base through factory auth/provider constructors with base URL normalization.

Phase 2: expand provider routing/auth tests (deepseek/nvidia/shengsuanyun, codex/claude oauth/codex-cli) and add openai_compat + anthropic coverage for proxy transport, model normalization, numeric option coercion, token-source refresh, and base URL behavior.

Phase 3: apply gofmt and validate with Dockerized tests (go test ./pkg/providers/... ./pkg/migrate and go test ./...).

pkg/providers/protocoltypes/types.go

@@ -0,0 +1,45 @@
+package protocoltypes
+
+type ToolCall struct {
+	ID        string                 `json:"id"`
+	Type      string                 `json:"type,omitempty"`
+	Function  *FunctionCall          `json:"function,omitempty"`
+	Name      string                 `json:"name,omitempty"`
+	Arguments map[string]interface{} `json:"arguments,omitempty"`
+}
+
+type FunctionCall struct {
+	Name      string `json:"name"`
+	Arguments string `json:"arguments"`
+}
+
+type LLMResponse struct {
+	Content      string     `json:"content"`
+	ToolCalls    []ToolCall `json:"tool_calls,omitempty"`
+	FinishReason string     `json:"finish_reason"`
+	Usage        *UsageInfo `json:"usage,omitempty"`
+}
+
+type UsageInfo struct {
+	PromptTokens     int `json:"prompt_tokens"`
+	CompletionTokens int `json:"completion_tokens"`
+	TotalTokens      int `json:"total_tokens"`
+}
+
+type Message struct {
+	Role       string     `json:"role"`
+	Content    string     `json:"content"`
+	ToolCalls  []ToolCall `json:"tool_calls,omitempty"`
+	ToolCallID string     `json:"tool_call_id,omitempty"`
+}
+
+type ToolDefinition struct {
+	Type     string                 `json:"type"`
+	Function ToolFunctionDefinition `json:"function"`
+}
+
+type ToolFunctionDefinition struct {
+	Name        string                 `json:"name"`
+	Description string                 `json:"description"`
+	Parameters  map[string]interface{} `json:"parameters"`
+}