Eliminate spdlog dependency (#773)

Removes the vendored spdlog library (~12,000 lines) and replaces it with a purpose-built logging system in zencore (~1,800 lines). The new implementation provides the same functionality with fewer abstractions, no shared_ptr overhead, and full control over the logging pipeline.

### What changed

**New logging core in zencore/logging/:**
- LogMessage, Formatter, Sink, Logger, Registry - core abstractions matching spdlog's model but simplified
- AnsiColorStdoutSink - ANSI color console output (replaces spdlog stdout_color_sink)
- MsvcSink - OutputDebugString on Windows (replaces spdlog msvc_sink)
- AsyncSink - async logging via BlockingQueue worker thread (replaces spdlog async_logger)
- NullSink, MessageOnlyFormatter - utility types
- Thread-safe timestamp caching in formatters using RwLock

**Moved to zenutil/logging/:**
- FullFormatter - full log formatting with timestamp, logger name, level, source location, multiline alignment
- JsonFormatter - structured JSON log output
- RotatingFileSink - rotating file sink with atomic size tracking

**API changes:**
- Log levels are now an enum (LogLevel) instead of int, eliminating the zen::logging::level namespace
- LoggerRef no longer wraps shared_ptr - it holds a raw pointer with the registry owning lifetime
- Logger error handler is wired through Registry and propagated to all loggers on registration
- Logger::Log() now populates ThreadId on every message

**Cleanup:**
- Deleted thirdparty/spdlog/ entirely (110+ files)
- Deleted full_test_formatter (was ~80% duplicate of FullFormatter)
- Renamed snake_case classes to PascalCase (full_formatter -> FullFormatter, json_formatter -> JsonFormatter, sentry_sink -> SentrySink)
- Removed spdlog from xmake dependency graph

### Build / test impact

- zencore no longer depends on spdlog
- zenutil and zenvfs xmake.lua updated to drop spdlog dep
- zentelemetry xmake.lua updated to drop spdlog dep
- All existing tests pass, no test changes required beyond formatter class renames

1 files changed, 0 insertions, 144 deletions

diff --git a/thirdparty/spdlog/tests/test_create_dir.cpp b/thirdparty/spdlog/tests/test_create_dir.cpp
deleted file mode 100644
index fd040339c..000000000
--- a/thirdparty/spdlog/tests/test_create_dir.cpp
+++ /dev/null
@@ -1,144 +0,0 @@
-/*
- * This content is released under the MIT License as specified in
- * https://raw.githubusercontent.com/gabime/spdlog/master/LICENSE
- */
-#include "includes.h"
-
-using spdlog::details::os::create_dir;
-using spdlog::details::os::path_exists;
-
-bool try_create_dir(const spdlog::filename_t &path, const spdlog::filename_t &normalized_path) {
-    auto rv = create_dir(path);
-    REQUIRE(rv == true);
-    return path_exists(normalized_path);
-}
-
-TEST_CASE("create_dir", "[create_dir]") {
-    prepare_logdir();
-
-    REQUIRE(try_create_dir(SPDLOG_FILENAME_T("test_logs/dir1/dir1"),
-                           SPDLOG_FILENAME_T("test_logs/dir1/dir1")));
-    REQUIRE(try_create_dir(SPDLOG_FILENAME_T("test_logs/dir1/dir1"),
-                           SPDLOG_FILENAME_T("test_logs/dir1/dir1")));  // test existing
-    REQUIRE(try_create_dir(SPDLOG_FILENAME_T("test_logs/dir1///dir2//"),
-                           SPDLOG_FILENAME_T("test_logs/dir1/dir2")));
-    REQUIRE(try_create_dir(SPDLOG_FILENAME_T("./test_logs/dir1/dir3"),
-                           SPDLOG_FILENAME_T("test_logs/dir1/dir3")));
-    REQUIRE(try_create_dir(SPDLOG_FILENAME_T("test_logs/../test_logs/dir1/dir4"),
-                           SPDLOG_FILENAME_T("test_logs/dir1/dir4")));
-
-#ifdef WIN32
-    // test backslash folder separator
-    REQUIRE(try_create_dir(SPDLOG_FILENAME_T("test_logs\\dir1\\dir222"),
-                           SPDLOG_FILENAME_T("test_logs\\dir1\\dir222")));
-    REQUIRE(try_create_dir(SPDLOG_FILENAME_T("test_logs\\dir1\\dir223\\"),
-                           SPDLOG_FILENAME_T("test_logs\\dir1\\dir223\\")));
-    REQUIRE(try_create_dir(SPDLOG_FILENAME_T(".\\test_logs\\dir1\\dir2\\dir99\\..\\dir23"),
-                           SPDLOG_FILENAME_T("test_logs\\dir1\\dir2\\dir23")));
-    REQUIRE(try_create_dir(SPDLOG_FILENAME_T("test_logs\\..\\test_logs\\dir1\\dir5"),
-                           SPDLOG_FILENAME_T("test_logs\\dir1\\dir5")));
-#endif
-}
-
-TEST_CASE("create_invalid_dir", "[create_dir]") {
-    REQUIRE(create_dir(SPDLOG_FILENAME_T("")) == false);
-    REQUIRE(create_dir(spdlog::filename_t{}) == false);
-#ifdef __linux__
-    REQUIRE(create_dir("/proc/spdlog-utest") == false);
-#endif
-}
-
-TEST_CASE("dir_name", "[create_dir]") {
-    using spdlog::details::os::dir_name;
-    REQUIRE(dir_name(SPDLOG_FILENAME_T("")).empty());
-    REQUIRE(dir_name(SPDLOG_FILENAME_T("dir")).empty());
-
-#ifdef WIN32
-    REQUIRE(dir_name(SPDLOG_FILENAME_T(R"(dir\)")) == SPDLOG_FILENAME_T("dir"));
-    REQUIRE(dir_name(SPDLOG_FILENAME_T(R"(dir\\\)")) == SPDLOG_FILENAME_T(R"(dir\\)"));
-    REQUIRE(dir_name(SPDLOG_FILENAME_T(R"(dir\file)")) == SPDLOG_FILENAME_T("dir"));
-    REQUIRE(dir_name(SPDLOG_FILENAME_T(R"(dir/file)")) == SPDLOG_FILENAME_T("dir"));
-    REQUIRE(dir_name(SPDLOG_FILENAME_T(R"(dir\file.txt)")) == SPDLOG_FILENAME_T("dir"));
-    REQUIRE(dir_name(SPDLOG_FILENAME_T(R"(dir/file)")) == SPDLOG_FILENAME_T("dir"));
-    REQUIRE(dir_name(SPDLOG_FILENAME_T(R"(dir\file.txt\)")) ==
-            SPDLOG_FILENAME_T(R"(dir\file.txt)"));
-    REQUIRE(dir_name(SPDLOG_FILENAME_T(R"(\dir\file.txt)")) == SPDLOG_FILENAME_T(R"(\dir)"));
-    REQUIRE(dir_name(SPDLOG_FILENAME_T(R"(\\dir\file.txt)")) == SPDLOG_FILENAME_T(R"(\\dir)"));
-    REQUIRE(dir_name(SPDLOG_FILENAME_T(R"(..\file.txt)")) == SPDLOG_FILENAME_T(".."));
-    REQUIRE(dir_name(SPDLOG_FILENAME_T(R"(.\file.txt)")) == SPDLOG_FILENAME_T("."));
-    REQUIRE(dir_name(SPDLOG_FILENAME_T(R"(c:\\a\b\c\d\file.txt)")) ==
-            SPDLOG_FILENAME_T(R"(c:\\a\b\c\d)"));
-    REQUIRE(dir_name(SPDLOG_FILENAME_T(R"(c://a/b/c/d/file.txt)")) ==
-            SPDLOG_FILENAME_T(R"(c://a/b/c/d)"));
-#endif
-    REQUIRE(dir_name(SPDLOG_FILENAME_T("dir/")) == SPDLOG_FILENAME_T("dir"));
-    REQUIRE(dir_name(SPDLOG_FILENAME_T("dir///")) == SPDLOG_FILENAME_T("dir//"));
-    REQUIRE(dir_name(SPDLOG_FILENAME_T("dir/file")) == SPDLOG_FILENAME_T("dir"));
-    REQUIRE(dir_name(SPDLOG_FILENAME_T("dir/file.txt")) == SPDLOG_FILENAME_T("dir"));
-    REQUIRE(dir_name(SPDLOG_FILENAME_T("dir/file.txt/")) == SPDLOG_FILENAME_T("dir/file.txt"));
-    REQUIRE(dir_name(SPDLOG_FILENAME_T("/dir/file.txt")) == SPDLOG_FILENAME_T("/dir"));
-    REQUIRE(dir_name(SPDLOG_FILENAME_T("//dir/file.txt")) == SPDLOG_FILENAME_T("//dir"));
-    REQUIRE(dir_name(SPDLOG_FILENAME_T("../file.txt")) == SPDLOG_FILENAME_T(".."));
-    REQUIRE(dir_name(SPDLOG_FILENAME_T("./file.txt")) == SPDLOG_FILENAME_T("."));
-}
-
-#ifdef _WIN32
-
-    //
-    // test windows cases when drive letter is given e.g. C:\\some-folder
-    //
-    #include <windows.h>
-    #include <fileapi.h>
-
-std::string get_full_path(const std::string &relative_folder_path) {
-    char full_path[MAX_PATH];
-
-    DWORD result = ::GetFullPathNameA(relative_folder_path.c_str(), MAX_PATH, full_path, nullptr);
-    // Return an empty string if failed to get full path
-    return result > 0 && result < MAX_PATH ? std::string(full_path) : std::string();
-}
-
-std::wstring get_full_path(const std::wstring &relative_folder_path) {
-    wchar_t full_path[MAX_PATH];
-    DWORD result = ::GetFullPathNameW(relative_folder_path.c_str(), MAX_PATH, full_path, nullptr);
-    return result > 0 && result < MAX_PATH ? std::wstring(full_path) : std::wstring();
-}
-
-spdlog::filename_t::value_type find_non_existing_drive() {
-    for (char drive = 'A'; drive <= 'Z'; ++drive) {
-        std::string root_path = std::string(1, drive) + ":\\";
-        UINT drive_type = GetDriveTypeA(root_path.c_str());
-        if (drive_type == DRIVE_NO_ROOT_DIR) {
-            return static_cast<spdlog::filename_t::value_type>(drive);
-        }
-    }
-    return '\0';  // No available drive found
-}
-
-TEST_CASE("create_abs_path1", "[create_dir]") {
-    prepare_logdir();
-    auto abs_path = get_full_path(SPDLOG_FILENAME_T("test_logs\\logdir1"));
-    REQUIRE(!abs_path.empty());
-    REQUIRE(create_dir(abs_path) == true);
-}
-
-TEST_CASE("create_abs_path2", "[create_dir]") {
-    prepare_logdir();
-    auto abs_path = get_full_path(SPDLOG_FILENAME_T("test_logs/logdir2"));
-    REQUIRE(!abs_path.empty());
-    REQUIRE(create_dir(abs_path) == true);
-}
-
-TEST_CASE("non_existing_drive", "[create_dir]") {
-    prepare_logdir();
-    spdlog::filename_t path;
-
-    auto non_existing_drive = find_non_existing_drive();
-    path += non_existing_drive;
-    path += SPDLOG_FILENAME_T(":\\");
-    REQUIRE(create_dir(path) == false);
-    path += SPDLOG_FILENAME_T("subdir");
-    REQUIRE(create_dir(path) == false);
-}
-// #endif  // SPDLOG_WCHAR_FILENAMES
-#endif  // _WIN32