feat(robot_agent): 基于 libhttp 的 DeepSeek 视觉机器人 agent 骨架

- 工具循环：capture_image / get_robot_status / spawn_subagent
- 子代理：技能超集（run_command 带超时截断、read_file / write_file）
- V4L2 摄像头抓帧：MJPEG 优先零转码，YUYV+libjpeg 回退，/dev/video* 自动探测
- 时间戳注入：system prompt 会话级当前时间 + 工具结果执行时间
- CLI：--prompt-file / --camera / --camera-device / --model / --max-turns

robot_agent/agent.cpp

@@ -0,0 +1,153 @@
+#include "agent.hpp"
+
+#include <us/HttpClient.hpp>
+
+#include <ctime>
+#include <iostream>
+#include <stdexcept>
+
+using pmc::net::HttpClient;
+
+namespace {
+
+// 本地时间 ISO8601，如 2026-08-21T14:30:05+08:00
+std::string now_iso8601() {
+    std::time_t tt = std::chrono::system_clock::to_time_t(std::chrono::system_clock::now());
+    std::tm tm{};
+    localtime_r(&tt, &tm);
+    char buf[64];
+    strftime(buf, sizeof(buf), "%Y-%m-%dT%H:%M:%S%z", &tm);
+    std::string s(buf);
+    if (s.size() >= 5 && (s[s.size() - 5] == '+' || s[s.size() - 5] == '-'))
+        s.insert(s.size() - 2, ":");
+    return s;
+}
+
+} // namespace
+
+json::object user_text_msg(const std::string& text) {
+    return json::object{{"role", "user"}, {"content", text}};
+}
+
+json::object user_image_msg(const std::string& text, const std::string& data_url) {
+    return json::object{
+        {"role", "user"},
+        {"content", json::array{
+            json::object{{"type", "text"}, {"text", text}},
+            json::object{{"type", "image_url"},
+                         {"image_url", json::object{{"url", data_url}}}},
+        }},
+    };
+}
+
+json::object tool_result_msg(const std::string& call_id, const std::string& text) {
+    return json::object{{"role", "tool"}, {"tool_call_id", call_id}, {"content", text}};
+}
+
+json::value build_tools_spec(const ToolRegistry& registry) {
+    json::array arr;
+    for (const auto& t : registry.all()) {
+        arr.push_back(json::object{
+            {"type", "function"},
+            {"function", json::object{
+                {"name", t.name},
+                {"description", t.description},
+                {"parameters", t.parameters},
+            }},
+        });
+    }
+    return arr;
+}
+
+std::string run_chat_loop(const AgentConfig& cfg,
+                          const std::string& system_prompt,
+                          const std::string& user_question,
+                          const ToolRegistry& registry,
+                          const std::string& log_tag) {
+    json::array messages;
+    // 会话开始注入一次当前时间（会话内保持不变，避免模型混淆"现在"）
+    std::string timed_prompt =
+        system_prompt + "\n当前时间: " + now_iso8601() + "（本会话内保持不变）";
+    messages.push_back(json::object{{"role", "system"}, {"content", timed_prompt}});
+    messages.push_back(user_text_msg(user_question));
+
+    HttpClient client;
+    client.set_header("Authorization: Bearer " + cfg.api_key);
+    client.set_header("Content-Type: application/json");
+
+    for (int turn = 0; turn < cfg.max_turns; ++turn) {
+        json::object body;
+        body["model"] = cfg.model;
+        body["messages"] = messages;
+        body["tools"] = build_tools_spec(registry);
+        body["stream"] = false;
+
+        std::string response_body;
+        client.post_stream_sync(cfg.endpoint, json::serialize(body),
+                                [&](const std::string& chunk) { response_body += chunk; });
+
+        long code = client.get_response_code();
+        if (code != 200)
+            throw std::runtime_error("HTTP " + std::to_string(code) + ": " + response_body);
+
+        json::error_code ec;
+        json::value resp = json::parse(response_body, ec);
+        if (ec)
+            throw std::runtime_error("响应不是合法 JSON: " + response_body.substr(0, 200));
+        if (resp.as_object().contains("error"))
+            throw std::runtime_error("API 错误: " + json::serialize(resp.at("error")));
+
+        auto& choices = resp.at("choices").as_array();
+        if (choices.empty()) throw std::runtime_error("响应中没有 choices");
+        auto& message = choices[0].as_object().at("message").as_object();
+
+        auto tc_it = message.find("tool_calls");
+        bool has_tool_calls = tc_it != message.end() && !tc_it->value().is_null() &&
+                              !tc_it->value().as_array().empty();
+
+        if (has_tool_calls) {
+            messages.push_back(message); // 回传 assistant 的 tool_calls 消息
+
+            for (const auto& call : tc_it->value().as_array()) {
+                const auto& c = call.as_object();
+                std::string call_id =
+                    c.contains("id") ? json::value_to<std::string>(c.at("id")) : "";
+                const auto& fn = c.at("function").as_object();
+                std::string name = json::value_to<std::string>(fn.at("name"));
+
+                json::value args;
+                auto args_it = fn.find("arguments");
+                if (args_it != fn.end() && !args_it->value().is_null()) {
+                    std::string args_str = json::value_to<std::string>(args_it->value());
+                    json::error_code aec;
+                    args = json::parse(args_str, aec);
+                    if (aec) args = json::object();
+                } else {
+                    args = json::object();
+                }
+
+                ToolResult result;
+                if (!registry.execute(name, args, result))
+                    result = {"错误: 未知工具 " + name, ""};
+
+                // 工具结果统一附执行时间戳，供模型判断数据新旧
+                std::string timed_result = "工具执行时间: " + now_iso8601() + "\n" + result.text;
+                std::cerr << "[" << log_tag << "][工具] " << name << " → "
+                          << timed_result.substr(0, 120) << "\n";
+                messages.push_back(tool_result_msg(call_id, timed_result));
+                if (!result.image_data_url.empty())
+                    messages.push_back(
+                        user_image_msg("工具返回的图片如下，请结合图片继续回答。",
+                                       result.image_data_url));
+            }
+            continue;
+        }
+
+        if (message.contains("content") && message.at("content").is_string())
+            return json::value_to<std::string>(message.at("content"));
+        throw std::runtime_error("模型没有返回文本内容");
+    }
+
+    throw std::runtime_error("达到最大工具轮次 (" + std::to_string(cfg.max_turns) +
+                             ")，未获得最终回答");
+}