Add step 624 in-editor agent chat panel model

editor/src/AgentChatPanelModel.h

@@ -0,0 +1,74 @@
+#pragma once
+// Step 624: Agent Chat Panel model
+
+#include <cctype>
+#include <string>
+#include <vector>
+
+enum class AgentChatRole {
+    User,
+    Assistant,
+    Tool
+};
+
+struct AgentChatMessage {
+    AgentChatRole role = AgentChatRole::User;
+    std::string content;
+    std::string timestamp;
+};
+
+struct AgentChatState {
+    std::vector<AgentChatMessage> messages;
+    std::string draftInput;
+    bool autoScroll = true;
+    bool open = false;
+};
+
+class AgentChatPanelModel {
+public:
+    static bool sendUserMessage(AgentChatState* state, const std::string& timestamp) {
+        if (!state) return false;
+        std::string text = trimCopy(state->draftInput);
+        if (text.empty()) return false;
+        state->messages.push_back({AgentChatRole::User, text, timestamp});
+        state->draftInput.clear();
+        state->autoScroll = true;
+        return true;
+    }
+
+    static void addAssistantMessage(AgentChatState* state,
+                                    const std::string& content,
+                                    const std::string& timestamp) {
+        if (!state) return;
+        state->messages.push_back({AgentChatRole::Assistant, content, timestamp});
+        state->autoScroll = true;
+    }
+
+    static void addToolMessage(AgentChatState* state,
+                               const std::string& content,
+                               const std::string& timestamp) {
+        if (!state) return;
+        state->messages.push_back({AgentChatRole::Tool, content, timestamp});
+        state->autoScroll = true;
+    }
+
+    static const char* roleLabel(AgentChatRole role) {
+        if (role == AgentChatRole::User) return "user";
+        if (role == AgentChatRole::Assistant) return "assistant";
+        return "tool";
+    }
+
+    static std::string trimCopy(const std::string& value) {
+        std::size_t begin = 0;
+        while (begin < value.size() &&
+               std::isspace(static_cast<unsigned char>(value[begin]))) {
+            ++begin;
+        }
+        std::size_t end = value.size();
+        while (end > begin &&
+               std::isspace(static_cast<unsigned char>(value[end - 1]))) {
+            --end;
+        }
+        return value.substr(begin, end - begin);
+    }
+};