refactor(lexer): 重构词法分析器头文件结构并优化缓冲区管理

移除了旧的lexer_stream.c实现，引入新的环形缓冲区机制来替代原有的
动态数组缓冲区。更新了词法分析器的核心数据结构，修改了token获取
相关函数的实现以支持新的缓冲区管理方式。

BREAKING CHANGE: 移除了scc_lexer_stream_t相关的API，替换为基于
环形缓冲区的新接口scc_lexer_to_ring和相关函数。

feat(lexer_token): 添加词法分析结果内存泄漏警告注释

docs: 移除预处理器模块的测试文件和相关配置

libs/sstream/src/main.c

@@ -1,51 +0,0 @@
-#include "scc_sstream.h"
-#include <stdio.h>
-
-int main(int argc, char **argv) {
-    const char *filename = (argc > 1) ? argv[1] : __FILE__; // 默认读取自身
-    scc_sstream_t stream;
-    scc_sstream_ring_t *ring;
-
-    // 初始化
-    if (scc_sstream_init(&stream, filename, 16) != 0) {
-        fprintf(stderr, "Failed to initialize stream for %s\n", filename);
-        return 1;
-    }
-    ring = scc_sstream_ref_ring(&stream);
-    Assert(ring != null);
-
-    printf("Reading file: %s\n", filename);
-
-    scc_sstream_char_t elem;
-    cbool ok;
-    int char_count = 0;
-    int line_count = 0;
-
-    // 循环读取所有字符
-    while (1) {
-        scc_ring_next_consume(*ring, elem, ok);
-        if (!ok)
-            break; // 文件结束或错误
-
-        char_count++;
-        if (elem.character == '\n')
-            line_count++;
-
-        // 打印前 200 个字符的位置信息（避免刷屏）
-        if (char_count <= 200) {
-            printf("char[%d]: '%c' (line %zu, col %zu)\n", char_count,
-                   elem.character == '\n' ? ' '
-                                          : elem.character, // 换行符显示为空格
-                   elem.pos.line, elem.pos.col);
-        }
-    }
-
-    printf("\nSummary:\n");
-    printf("  Total characters: %d\n", char_count);
-    printf("  Total lines: %d\n", line_count);
-
-    // 释放资源
-    scc_sstream_drop_ring(ring);
-    scc_sstream_drop(&stream);
-    return 0;
-}

libs/sstream/src/scc_sstream.c

@@ -66,7 +66,7 @@ static int sstream_scan_at(scc_sstream_t *stream, scc_pos_t scan_pos,
 }
 
 // 环形缓冲区填充回调（通过 userdata 获取流对象）
-static cbool fill_func(scc_sstream_char_t *out, void *userdata) {
+static int fill_func(scc_sstream_char_t *out, void *userdata) {
     scc_sstream_t *stream = (scc_sstream_t *)userdata;
     if (stream->fill_pos.offset >= stream->len)
         return false; // 已到文件尾
@@ -82,6 +82,10 @@ static cbool fill_func(scc_sstream_char_t *out, void *userdata) {
 int scc_sstream_init(scc_sstream_t *stream, const char *fname, int ring_size) {
     Assert(stream != null && fname != null);
     scc_file_t file = scc_fopen(fname, SCC_FILE_READ);
+    if (file == null) {
+        LOG_ERROR("Failed to open file: %s", fname);
+        return 0;
+    }
     usize fsize = scc_fsize(file);
     if (fsize == 0) {
         LOG_WARN("file size is 0");
@@ -115,7 +119,7 @@ int scc_sstream_init_by_buffer(scc_sstream_t *stream, const char *buffer,
     return 0;
 }
 
-scc_sstream_ring_t *scc_sstream_ref_ring(scc_sstream_t *stream) {
+scc_sstream_ring_t *scc_sstream_to_ring(scc_sstream_t *stream) {
     Assert(stream != null);
     stream->used++;
     return &stream->ring;