feat(ast): 添加AST定义和dump工具头文件

新增libs/ast模块的基础定义文件，包括：
- AST节点类型枚举定义，涵盖声明、语句、表达式、类型等各类节点
- AST操作符枚举，定义所有二元、一元、逻辑、算术等操作符
- AST节点结构体定义，包含表达式、语句、声明、类型等具体实现
- AST dump工具接口，支持树形结构输出和颜色显示
- 语义分析回调函数类型定义，为后续语义分析提供基础

libs/parser/src/parser.c

@@ -0,0 +1,85 @@
+/**
+ * @file parser.c
+ * @brief 新的解析器实现
+ */
+
+#include "parser.h"
+#include <log.h>
+
+static void dummy_sema_callback(void *context, scc_ast_node_type_t node_type,
+                                void *node) {
+    (void)context;
+    (void)node_type;
+    (void)node;
+    return;
+}
+
+#define ASSIGN_PTR_OR_DEFAULT(assigned_val, value, default)                    \
+    assigned_val = value ? value : default
+
+void scc_parser_init(scc_parser_t *parser, scc_lexer_stream_t *lexer,
+                     scc_sema_callbacks_t *callbacks) {
+    Assert(parser != null && lexer != null);
+    parser->lex_stream = lexer;
+    parser->has_error = false;
+    parser->translation_unit = null;
+    if (callbacks) {
+        ASSIGN_PTR_OR_DEFAULT(parser->sema_callbacks.on_decl,
+                              callbacks->on_decl, dummy_sema_callback);
+        ASSIGN_PTR_OR_DEFAULT(parser->sema_callbacks.on_stmt,
+                              callbacks->on_stmt, dummy_sema_callback);
+        ASSIGN_PTR_OR_DEFAULT(parser->sema_callbacks.on_expr,
+                              callbacks->on_expr, dummy_sema_callback);
+        ASSIGN_PTR_OR_DEFAULT(parser->sema_callbacks.on_type,
+                              callbacks->on_type, dummy_sema_callback);
+        parser->sema_callbacks.context = callbacks->context;
+    } else {
+        parser->sema_callbacks.on_decl = dummy_sema_callback;
+        parser->sema_callbacks.on_stmt = dummy_sema_callback;
+        parser->sema_callbacks.on_expr = dummy_sema_callback;
+        parser->sema_callbacks.on_type = dummy_sema_callback;
+        parser->sema_callbacks.context = dummy_sema_callback;
+    }
+    // // ONLY FOR INIT TYPE
+    // parser->current_token.type = SCC_TOK_UNKNOWN;
+}
+
+void scc_parser_drop(scc_parser_t *parser) {
+    // TODO: 释放 AST 内存
+    (void)parser;
+}
+
+scc_ast_translation_unit_t *scc_parse_translation_unit(scc_parser_t *parser) {
+    scc_ast_translation_unit_t *unit =
+        scc_malloc(sizeof(scc_ast_translation_unit_t));
+    if (!unit)
+        return null;
+    unit->base.type = SCC_AST_TRANSLATION_UNIT;
+    scc_vec_init(unit->declarations);
+
+    /**
+     * Program := (Declaration | Definition)*
+     * same as
+     * Program := Declaration* Definition*
+     */
+    do {
+        scc_ast_decl_t *decl = scc_parse_declaration(parser);
+        if (decl != null) {
+            scc_vec_push(unit->declarations, decl);
+        } else {
+            break;
+            // MAYBE return or next
+        }
+    } while (!scc_lexer_tok_match(scc_lexer_stream_current(parser->lex_stream),
+                                  SCC_TOK_EOF) &&
+             !parser->has_error);
+
+    if (parser->has_error) {
+        // TODO: 清理
+        scc_free(unit);
+        return null;
+    }
+
+    Assert(unit->base.type == SCC_AST_TRANSLATION_UNIT);
+    return unit;
+}