fix: remove tool call ID truncation and improve DeepSeek reasoning handling

The 40-character truncation of tool call IDs in helper.go caused collisions
when models (like deepseek-v4-flash) generated longer IDs, leading to
"Duplicate value for 'tool_call_id'" errors. Removed the limit to allow
full unique IDs.

DeepSeek: updated reasoning_content injection to use an empty string
instead of a space, better matching provider expectations for history.

Improved API error reporting across all providers by capturing raw body
content when response parsing fails or returns empty strings.

internal/providers/openai.go

@@ -4,6 +4,8 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"io"
+	"log"
 	"strings"
 	"time"
 
@@ -38,6 +40,17 @@ func (p *OpenAIProvider) ChatCompletion(ctx context.Context, req *models.Unified
 
 	body := BuildOpenAIBody(req, messagesJSON, false)
 
+	// Debug message sequence
+	for i, m := range messagesJSON {
+		mMap, _ := m.(map[string]interface{})
+		role, _ := mMap["role"].(string)
+		hasToolCalls := false
+		if tc, ok := mMap["tool_calls"]; ok && tc != nil {
+			hasToolCalls = true
+		}
+		log.Printf("[DEBUG] OpenAI Msg[%d]: role=%s, hasToolCalls=%v", i, role, hasToolCalls)
+	}
+
 	// Transition: Newer models require max_completion_tokens
 	if strings.HasPrefix(req.Model, "o1-") || strings.HasPrefix(req.Model, "o3-") || strings.Contains(req.Model, "gpt-5") {
 		if maxTokens, ok := body["max_tokens"]; ok {
@@ -57,7 +70,14 @@ func (p *OpenAIProvider) ChatCompletion(ctx context.Context, req *models.Unified
 	}
 
 	if !resp.IsSuccess() {
-		return nil, fmt.Errorf("OpenAI API error (%d): %s", resp.StatusCode(), resp.String())
+		msg := resp.String()
+		if msg == "" {
+			if body, err := io.ReadAll(resp.RawBody()); err == nil {
+				msg = string(body)
+			}
+		}
+		log.Printf("OpenAI API Error (%d): %s", resp.StatusCode(), msg)
+		return nil, fmt.Errorf("OpenAI API error (%d): %s", resp.StatusCode(), msg)
 	}
 
 	var respJSON map[string]interface{}
@@ -104,7 +124,13 @@ func (p *OpenAIProvider) ImageGeneration(ctx context.Context, req *models.ImageG
 	}
 
 	if !resp.IsSuccess() {
-		return nil, fmt.Errorf("OpenAI image API error (%d): %s", resp.StatusCode(), resp.String())
+		msg := resp.String()
+		if msg == "" {
+			if body, err := io.ReadAll(resp.RawBody()); err == nil {
+				msg = string(body)
+			}
+		}
+		return nil, fmt.Errorf("OpenAI image API error (%d): %s", resp.StatusCode(), msg)
 	}
 
 	var result models.ImageGenerationResponse
@@ -123,6 +149,17 @@ func (p *OpenAIProvider) ChatCompletionStream(ctx context.Context, req *models.U
 
 	body := BuildOpenAIBody(req, messagesJSON, true)
 
+	// Debug message sequence
+	for i, m := range messagesJSON {
+		mMap, _ := m.(map[string]interface{})
+		role, _ := mMap["role"].(string)
+		hasToolCalls := false
+		if tc, ok := mMap["tool_calls"]; ok && tc != nil {
+			hasToolCalls = true
+		}
+		log.Printf("[DEBUG] OpenAI Stream Msg[%d]: role=%s, hasToolCalls=%v", i, role, hasToolCalls)
+	}
+
 	// Transition: Newer models require max_completion_tokens
 	if strings.HasPrefix(req.Model, "o1-") || strings.HasPrefix(req.Model, "o3-") || strings.Contains(req.Model, "gpt-5") {
 		if maxTokens, ok := body["max_tokens"]; ok {
@@ -143,7 +180,14 @@ func (p *OpenAIProvider) ChatCompletionStream(ctx context.Context, req *models.U
 	}
 
 	if !resp.IsSuccess() {
-		return nil, fmt.Errorf("OpenAI API error (%d): %s", resp.StatusCode(), resp.String())
+		msg := resp.String()
+		if msg == "" {
+			if body, err := io.ReadAll(resp.RawBody()); err == nil {
+				msg = string(body)
+			}
+		}
+		log.Printf("OpenAI API Error (%d): %s", resp.StatusCode(), msg)
+		return nil, fmt.Errorf("OpenAI API error (%d): %s", resp.StatusCode(), msg)
 	}
 
 	ch := make(chan *models.ChatCompletionStreamResponse)