v0.20.0: thinking blocks, chat windows overhaul, scroll fix

Backend:
- Add isThinking flag to agentEvent for text before tool calls
- Separate thinking from response text in runChatTurn and continue.go
- Persist thinking in a dedicated field in message content

Frontend:
- Add thinking field to MessageContent, ChatMessage, ChatTextEvent types
- Create ThinkingBlock.svelte — collapsible block with brain icon
- SSE handler moves text_delta content to thinking on isThinking flag
- Render thinking block between tools and response in ChatThread
- Fix chat window scroll reset on focus change (stable windowKeys order)
- Remove redundant #key id wrapper in WindowLayer
- Enlarge sidebar rail (24→32 default, 40→60 max)
- Remove glyph from sidebar, square graph at top
- Replace AgentTrace/ToolCallCard/UnifiedTimeline with TurnTrace/ToolLine

cmd/nomos/agent.go

@@ -181,6 +181,11 @@ type agentEvent struct {
 	Data      any    `json:"data,omitempty"`
 	SessionID string `json:"session_id,omitempty"`
 	Iteration int    `json:"iteration,omitempty"`
+	// IsThinking marks text/text_delta events that carry the model's internal
+	// reasoning (text produced before tool calls in the same iteration), as
+	// distinct from the final response text. The frontend renders these as
+	// collapsible thinking blocks separated from the response.
+	IsThinking bool `json:"is_thinking,omitempty"`
 }
 
 func (a *agent) chat(ctx context.Context, sessionID, message string, emit func(agentEvent)) {
@@ -465,7 +470,7 @@ func (a *agent) chatWith(ctx context.Context, sessionID, message, systemInject s
 		// led to each step. Emitting it lets the persist layer accumulate
 		// per-iteration reasoning into the row's text field.
 		if strings.TrimSpace(msg.Content) != "" {
-			emit(agentEvent{Type: "text", Data: msg.Content, SessionID: sessionID})
+			emit(agentEvent{Type: "text", Data: msg.Content, SessionID: sessionID, IsThinking: true})
 		}
 
 		slog.Info("nomos: tool calls", "count", len(msg.ToolCalls), "iter", i+1, "correlation", correlationID)

cmd/nomos/continue.go

@@ -242,6 +242,7 @@ func (a *agent) resumeSession(ctx context.Context, sessionID, note string) bool
 
 	var toolCalls []map[string]any
 	var finalText, errText string
+	var finalThinking string
 
 	persist := func() {
 		if msgID == uuid.Nil {
@@ -254,6 +255,7 @@ func (a *agent) resumeSession(ctx context.Context, sessionID, note string) bool
 		body, _ := json.Marshal(map[string]any{
 			"role":       "assistant",
 			"text":       text,
+			"thinking":   finalThinking,
 			"tool_calls": toolCalls,
 			"auto":       true, // marks this as an autonomous continuation, not an operator turn
 		})
@@ -289,10 +291,14 @@ func (a *agent) resumeSession(ctx context.Context, sessionID, note string) bool
 			}
 		}
 		toolCalls, finalText, errText = nil, "", ""
+		finalThinking = ""
 		// P3: accumulate per-iteration reasoning instead of overwriting
 		// (same fix as main.go's chat handler). Without this, a resumed
 		// turn's intermediate thinking is lost on reload.
+		// (same fix as main.go's chat handler). Without this, a resumed
+		// turn's intermediate thinking is lost on reload.
 		var textParts []string
+		var thinkingParts []string
 		emit := func(ev agentEvent) {
 			if ev.Type == "tool_use" || ev.Type == "tool_result" {
 				if m, ok := ev.Data.(map[string]any); ok {
@@ -319,8 +325,13 @@ func (a *agent) resumeSession(ctx context.Context, sessionID, note string) bool
 			}
 			if ev.Type == "text" {
 				if t, ok := ev.Data.(string); ok && t != "" {
-					textParts = append(textParts, t)
-					finalText = strings.Join(textParts, "\n\n")
+					if ev.IsThinking {
+						thinkingParts = append(thinkingParts, t)
+						finalThinking = strings.Join(thinkingParts, "\n\n")
+					} else {
+						textParts = append(textParts, t)
+						finalText = strings.Join(textParts, "\n\n")
+					}
 					persist()
 				}
 			}

cmd/nomos/main.go

@@ -180,7 +180,9 @@ func (a *agent) runChatTurn(pctx, ctx context.Context, sessionID, message string
 	// P3: accumulate per-iteration reasoning instead of overwriting with the
 	// final `text` event (see the original inline comment in handleChat).
 	var textParts []string
+	var thinkingParts []string
 	var finalText string
+	var finalThinking string
 
 	placeholder, _ := json.Marshal(map[string]any{"role": "assistant", "text": ""})
 	msgID, err := a.store.insertMessageReturningID(pctx, sessionID, "assistant", placeholder)
@@ -194,6 +196,7 @@ func (a *agent) runChatTurn(pctx, ctx context.Context, sessionID, message string
 		body, _ := json.Marshal(map[string]any{
 			"role":       "assistant",
 			"text":       finalText,
+			"thinking":   finalThinking,
 			"tool_calls": toolCalls,
 		})
 		a.store.updateMessage(pctx, msgID, body)
@@ -223,8 +226,13 @@ func (a *agent) runChatTurn(pctx, ctx context.Context, sessionID, message string
 		}
 		if ev.Type == "text" {
 			if t, ok := ev.Data.(string); ok && t != "" {
-				textParts = append(textParts, t)
-				finalText = strings.Join(textParts, "\n\n")
+				if ev.IsThinking {
+					thinkingParts = append(thinkingParts, t)
+					finalThinking = strings.Join(thinkingParts, "\n\n")
+				} else {
+					textParts = append(textParts, t)
+					finalText = strings.Join(textParts, "\n\n")
+				}
 				persist()
 			}
 		}