W17: extract ai_common shared module + fix anthropic data race + brace bugs

- New plugins_upper/ai_common/ static library: shared PluginConfig, ToolCallAccum,
  StreamContext, secure_zero, extract_host_port, serialize_tool_calls, free_chat_result
- Refactored openai/anthropic plugins to use dstalk_ai:: namespace from ai_common
- Fixed anthropic g_config raw pointer → std::atomic (data race)
- Added SSE parse error counter with threshold abort (kMaxSseParseErrors=5)
- Fixed missing closing brace in both plugins' error-body catch block
- Updated test targets: ai_common include path + link, using namespace dstalk_ai
- plugin_loader_test: added stub_unreg + service_registry.cpp for unregister_service
- Includes pre-existing uncommitted changes from prior waves

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

plugins_upper/ai_common/include/ai_common.hpp

@@ -0,0 +1,118 @@
+/*
+ * @file ai_common.hpp
+ * @brief Shared types and utilities for AI provider plugins (OpenAI / Anthropic).
+ * AI 提供者插件（OpenAI / Anthropic）的共享类型和工具函数。
+ * Copyright (c) 2026 dstalk contributors. GPLv3.
+ */
+
+#pragma once
+
+#include "dstalk/dstalk_host.h"
+#include "dstalk/dstalk_services.h"
+
+#include <boost/json.hpp>
+#include <string>
+#include <vector>
+
+namespace dstalk_ai {
+
+namespace json = boost::json;
+
+// ============================================================================
+// 共享类型 / Shared types
+// ============================================================================
+
+/// Provider connection configuration / 服务商连接配置
+struct PluginConfig {
+    std::string provider;
+    std::string base_url;
+    std::string api_key;
+    std::string model;
+    int max_tokens = 4096;
+    double temperature = 0.7;
+};
+
+/// Per-index tool-call accumulator for SSE streaming / SSE 流式传输的按索引工具调用累积器
+struct ToolCallAccum {
+    int index = -1;
+    std::string id;
+    std::string name;
+    std::string arguments;  // 增量拼接的 JSON arguments / incrementally concatenated JSON arguments
+};
+
+/// Streaming context passed through SSE callbacks / 通过 SSE 回调传递的流式上下文
+struct StreamContext {
+    const dstalk_host_api_t* host = nullptr;
+    dstalk_stream_cb user_cb = nullptr;
+    void* userdata = nullptr;
+    std::string accumulated;
+    std::vector<ToolCallAccum> tool_calls;
+    int sse_parse_errors = 0;        // 连续 SSE 解析错误计数器 / consecutive SSE parse error counter
+    bool streaming_ok = true;        // OpenAI: tracks stream health
+    bool saw_data_line = false;      // Anthropic: tracks if any SSE data received
+};
+
+/// Maximum consecutive SSE parse errors before aborting the stream / 中止流之前的最大连续 SSE 解析错误数
+inline constexpr int kMaxSseParseErrors = 5;
+
+// ============================================================================
+// 函数声明（实现于 ai_common.cpp） / Function declarations (implemented in ai_common.cpp)
+// ============================================================================
+
+/// Securely zero memory through volatile write to prevent compiler optimization.
+/// 通过 volatile 写入零来安全擦除内存，防止编译器优化。
+void secure_zero(void* p, size_t n);
+
+/// Parse a URL into scheme, host, port, and target path components.
+/// 将 URL 解析为 scheme、host、port 和 target path 组件。
+bool extract_host_port(const std::string& url,
+    std::string& scheme_out, std::string& host_out,
+    std::string& port_out, std::string& target_out);
+
+// ============================================================================
+// 内联工具函数 / Inline utility functions
+// ============================================================================
+
+/// Free all host-allocated string fields in a chat result struct.
+/// 释放 chat result 结构体中所有主机分配的字符串字段。
+inline void free_chat_result(const dstalk_host_api_t* host, dstalk_chat_result_t* result) {
+    if (!result || !host) return;
+    if (result->content)         { host->free((void*)result->content);         result->content = nullptr; }
+    if (result->error)           { host->free((void*)result->error);           result->error = nullptr; }
+    if (result->tool_calls_json) { host->free((void*)result->tool_calls_json); result->tool_calls_json = nullptr; }
+}
+
+/// Cache tools_json from the tools service for reuse in chat/chat_stream.
+/// 从 tools service 缓存 tools_json，供 chat/chat_stream 复用。
+inline void cache_tools_json(const dstalk_host_api_t* host, std::string& tools_json) {
+    if (!host) return;
+    auto* tools_svc = reinterpret_cast<const dstalk_tools_service_t*>(
+        host->query_service("tools", 1));
+    if (tools_svc && tools_svc->get_tools_json) {
+        char* j = tools_svc->get_tools_json();
+        if (j) {
+            tools_json = j;
+            host->free(j);
+        }
+    }
+}
+
+/// Serialize accumulated tool_calls into OpenAI-compatible JSON array.
+/// 将累积的 tool_calls 序列化为兼容 OpenAI 格式的 JSON 数组。
+inline std::string serialize_tool_calls(const std::vector<ToolCallAccum>& tool_calls) {
+    json::array tc_array;
+    for (const auto& tc : tool_calls) {
+        json::object tc_obj;
+        tc_obj["index"] = tc.index;
+        if (!tc.id.empty())   tc_obj["id"]   = tc.id;
+        tc_obj["type"] = "function";
+        json::object func;
+        if (!tc.name.empty()) func["name"] = tc.name;
+        func["arguments"] = tc.arguments;
+        tc_obj["function"] = func;
+        tc_array.push_back(std::move(tc_obj));
+    }
+    return json::serialize(tc_array);
+}
+
+} // namespace dstalk_ai