refactor(ast2ir): 移除废弃的ABI依赖并优化类型转换处理

移除了对scc_abi包的依赖，将相关头文件从libs/abi移动到libs/ast2ir目录下。
重构了基本类型解析功能，将parse_base_type函数提取为独立的
scc_ast2ir_parse_base_type实现，并支持有符号/无符号类型区分。

feat(ast2ir): 实现整数常量表达式求值器

新增了完整的整数常量表达式求值功能，支持C11标准中的常量表达式规则，
包括字面量、标识符、sizeof/_Alignof、一元/二元运算、条件表达式和
类型转换等操作。该功能用于数组大小和枚举值的编译期计算验证。

refactor(ast2ir): 完善类型提升和算术转换机制

改进了整数提升和寻常算术转换的实现，修复了移位操作的符号处理问题，
添加了无符号比较操作的支持，增强了类型安全检查，统一了错误处理流程。

fix(ast2ir): 修复赋值表达式返回值和数组大小计算问题

修正了赋值表达式的返回值处理，确保返回右侧值而不是存储指令引用。
使用新的常量表达式求值器替代原有的硬编码数组大小计算，提高了
数组声明的正确性。

tests/simple/test.py

@@ -7,6 +7,7 @@ executes the resulting binary, and validates the process return code or stdout.
 from __future__ import annotations
 
 import argparse
+import difflib
 import logging
 import os
 import subprocess
@@ -23,7 +24,8 @@ from typing import Sequence
 # Configuration
 # ---------------------------------------------------------------------------
 WORKSPACE = Path(__file__).resolve().parent
-CC_PATH = WORKSPACE / "../../build/dev/scc"
+CC_ROOT = WORKSPACE / "../.."
+CC_PATH = CC_ROOT / "build/dev/scc"
 CONFIG_PATH = WORKSPACE / "expect.toml"
 DEFAULT_TIMEOUT = 1  # seconds
 
@@ -99,8 +101,15 @@ class Runner:
                 text=True,
                 timeout=self.timeout,
             )
-        except subprocess.TimeoutExpired:
-            return False, "Compilation timed out"
+        except subprocess.TimeoutExpired as e:
+            # e.stdout, e.stderr 为已捕获的部分输出（字符串）
+            captured_stderr = e.stderr.strip() if e.stderr else ""
+            captured_stdout = e.stdout.strip() if e.stdout else ""
+            err_msg = f"""Compilation timed out.
+            stderr: {captured_stderr or '(no output)'}
+            stdout: {captured_stdout or '(no output)'}
+            cmd: {" ".join(cmd)}"""
+            return False, err_msg
         except OSError as exc:
             return False, f"Failed to invoke compiler: {exc}"
 
@@ -127,6 +136,26 @@ class Runner:
 
         return proc.returncode, proc.stdout, proc.stderr.strip()
 
+    def _print_diff(self, expected: str, actual: str) -> None:
+        """Print unified diff between expected and actual stdout."""
+        expected_lines = expected.splitlines()
+        actual_lines = actual.splitlines()
+        diff = difflib.unified_diff(
+            expected_lines, actual_lines,
+            fromfile='expected', tofile='actual',
+            lineterm=''
+        )
+        # diff = difflib.ndiff(
+        #     expected_lines, actual_lines,
+        # )
+        diff_lines = list(diff)
+        if not diff_lines:
+            logger.error("  Strings differ but no diff generated?")
+            return
+        logger.error("  Diff (expected vs actual):")
+        for line in diff_lines:
+            logger.error("    %s", line)
+
     def run_one(self, test: TestCase) -> bool:
         """Run a single test case. Returns True if passed."""
         logger.info("Testing %s", test.source)
@@ -157,9 +186,14 @@ class Runner:
         if passed:
             logger.info("  PASSED")
         else:
-            logger.error(
-                "  FAILED: expected %r, got %r", test.expected, actual
-            )
+            if test.test_type == "stdout":
+                logger.error("  FAILED: stdout mismatch")
+                self._print_diff(test.expected, actual)
+            else:
+                logger.error(
+                    "  FAILED: expected return code %r, got %r",
+                    test.expected, actual
+                )
 
         # 4. Cleanup
         self._remove(exe_path)
@@ -326,12 +360,12 @@ def main() -> None:
 
     runner = Runner(
         cc=args.cc,
-        workspace=WORKSPACE,
+        workspace=CC_ROOT,
         timeout=args.timeout,
         keep_temps=args.keep_temps,
     )
 
-    global_timeout = DEFAULT_TIMEOUT * 3
+    global_timeout = args.timeout * 3
     passed, total = runner.run_all(selected, global_timeout)
     logger.info("=" * 40)
     if global_timeout and total < len(selected):