feat: add support for Gemini thinking capabilities and simplify welcome UI

- Added `ThoughtSignature` and `ChunkTypeThinking` support for Google Gemini provider.
- Properly parse and accumulate Gemini thinking outputs.
- Echo `ThoughtSignature` back to Gemini in tool calls.
- Simplified the welcome UI by removing the bottom hint line and adjusting spacing.

Signed-off-by: Meng Yan <myan@redhat.com>

Author: yanmxa

internal/app/render/message.go

@@ -70,15 +70,7 @@ func RenderWelcome() string {
 		slashStyle.Render("/") +
 		bracketStyle.Render(">")
 
-	hintStyle := lipgloss.NewStyle().Foreground(theme.CurrentTheme.TextDisabled)
-
-	var sb strings.Builder
-	sb.WriteString("\n")
-	sb.WriteString(icon + "\n")
-	sb.WriteString("\n")
-	sb.WriteString("   " + hintStyle.Render("Enter to send · Esc to stop · Shift+Tab mode · Ctrl+C exit") + "\n")
-
-	return sb.String()
+	return "\n" + icon
 }
 
 // OperationModeParams holds the parameters needed for rendering mode status.

internal/app/view.go

@@ -82,10 +82,8 @@ func (m model) View() string {
 	var view strings.Builder
 	if chatSection != "" {
 		view.WriteString(chatSection)
-		view.WriteString("\n")
-	} else if m.conv.CommittedCount > 0 {
-		view.WriteString("\n")
 	}
+	view.WriteString("\n")
 	view.WriteString(separator)
 	view.WriteString("\n")
 	view.WriteString(inputView)

internal/message/message.go

@@ -52,9 +52,10 @@ type ImageData struct {
 
 // ToolCall represents a tool call from the model.
 type ToolCall struct {
-	ID    string `json:"id"`
-	Name  string `json:"name"`
-	Input string `json:"input"`
+	ID               string `json:"id"`
+	Name             string `json:"name"`
+	Input            string `json:"input"`
+	ThoughtSignature []byte `json:"thought_signature,omitempty"` // Google Gemini: opaque signature to echo back
 }
 
 // ToolResult represents the result of a tool execution.

internal/provider/google/client.go

@@ -85,13 +85,17 @@ func (c *Client) Stream(ctx context.Context, opts provider.CompletionOptions) <-
 							args = nil
 						}
 					}
-					parts = append(parts, &genai.Part{
+					p := &genai.Part{
 						FunctionCall: &genai.FunctionCall{
 							ID:   tc.ID,
 							Name: tc.Name,
 							Args: args,
 						},
-					})
+					}
+					if len(tc.ThoughtSignature) > 0 {
+						p.ThoughtSignature = tc.ThoughtSignature
+					}
+					parts = append(parts, p)
 				}
 			} else if len(msg.Images) > 0 {
 				// Multimodal message with images
@@ -184,13 +188,21 @@ func (c *Client) Stream(ctx context.Context, opts provider.CompletionOptions) <-
 				}
 
 				for _, part := range candidate.Content.Parts {
-					// Handle text
+					// Handle text (distinguish thinking from regular text)
 					if part.Text != "" {
-						ch <- message.StreamChunk{
-							Type: message.ChunkTypeText,
-							Text: part.Text,
+						if part.Thought {
+							ch <- message.StreamChunk{
+								Type: message.ChunkTypeThinking,
+								Text: part.Text,
+							}
+							response.Thinking += part.Text
+						} else {
+							ch <- message.StreamChunk{
+								Type: message.ChunkTypeText,
+								Text: part.Text,
+							}
+							response.Content += part.Text
 						}
-						response.Content += part.Text
 					}
 
 					// Handle function calls
@@ -211,9 +223,10 @@ func (c *Client) Stream(ctx context.Context, opts provider.CompletionOptions) <-
 						}
 
 						response.ToolCalls = append(response.ToolCalls, message.ToolCall{
-							ID:    fc.ID,
-							Name:  fc.Name,
-							Input: string(argsJSON),
+							ID:               fc.ID,
+							Name:             fc.Name,
+							Input:            string(argsJSON),
+							ThoughtSignature: part.ThoughtSignature,
 						})
 					}
 				}