chore(test): 初始化回归测试仓（新增 .gitignore，TestsOverview.md 改为 README.md）

把 Test/ 纳入 https://git.gvsds.com/GVSDS/Viper_RegressionTesting 。

1) 新增 .gitignore —— 只保留测试源码，剔除全部构建产物：
   目录   **/output*/（output / output_opt / output_orig / output_verify / output_dbg）、
          **/temp*/（temp / temp_opt）、**/.tpv_build/
   二进制 *.exe *.obj *.o *.out *.a *.lib *.dll
   中间物 *.ll *.vpi *.pyi *.deps.txt *.deps.json *.doc.json *_sha1_map.txt
          _pyi_cache_v1.pkl _pyi_cache_v1.sig.json _shared_sym.json _phase1_manifest.json
   其它   build_all.txt（构建日志）、*.log、__pycache__/、*.bak、IDE 目录
   保留   App/*.vp、project.json / project_opt.json / project.vpj、README.md、两个 .py
   实测 `git add -A --dry-run`：196 个文件，无任何构建产物混入。

2) TestsOverview.md → README.md（作为仓库首页文档）。

3) SequentialRegressionTest.py：7 处 TestsOverview.md 引用同步改为 README.md
   （文档串、OVERVIEW 路径、read_test_order 文档与报错文案、argparse description、
   启动横幅）；同时修正入口路径 PROJECTRANS —— 旧值 <root>/Projectrans.py 已不存在，
   改为 <root>/TransPyC/Projectrans.py（与 regression_test.py:45-48 记录一致），
   否则本脚本会以 "can't open file" 全量失败。
   regression_test.py 无需改动：它按目录扫描 project.json 找项目，不引用该文档。

StringTest/App/main.vp

@@ -0,0 +1,85 @@
+import t
+import stdio
+import string
+import testcheck
+import w32.win32memory
+
+def test_strlen():
+    testcheck.section("Test 1: strlen")
+    s: t.CChar | t.CPtr = "Hello, World!"
+    length: t.CUInt64T = string.strlen(s)
+    testcheck.check(length == 13, "strlen (len=13)", "strlen (expect 13)")
+
+def test_strcpy():
+    testcheck.section("Test 2: strcpy")
+    buf: t.CChar | t.CPtr = w32.win32memory.VirtualAlloc(None, 64, 12288, 4)
+    if t.CUInt64T(buf) == 0:
+        stdio.printf("SKIP: VirtualAlloc returned NULL\n")
+        return
+    string.memset(buf, 0, 64)
+    string.strcpy(buf, "test string")
+    cmp_result: t.CInt = string.strcmp(buf, "test string")
+    testcheck.check(cmp_result == 0, "strcpy (result=test string)", "strcpy (cmp mismatch)")
+
+def test_strcat():
+    testcheck.section("Test 3: strcat (via memcpy)")
+    buf: t.CChar | t.CPtr = w32.win32memory.VirtualAlloc(None, 64, 12288, 4)
+    if t.CUInt64T(buf) == 0:
+        stdio.printf("SKIP: VirtualAlloc returned NULL\n")
+        return
+    string.memset(buf, 0, 64)
+    # 手动拼接: 先拷贝 "Hello"，再拷贝 " World"
+    hello: t.CChar | t.CPtr = "Hello"
+    world: t.CChar | t.CPtr = " World"
+    string.memcpy(buf, hello, 5)
+    string.memcpy(t.CPtr(t.CUInt64T(buf) + 5), world, 6)
+    cmp_result: t.CInt = string.strcmp(buf, "Hello World")
+    testcheck.check(cmp_result == 0, "strcat via memcpy", "strcat via memcpy (cmp mismatch)")
+
+def test_strcmp():
+    testcheck.section("Test 4: strcmp")
+    r1: t.CInt = string.strcmp("abc", "abc")
+    r2: t.CInt = string.strcmp("abc", "abd")
+    r3: t.CInt = string.strcmp("abd", "abc")
+    testcheck.check(r1 == 0 and r2 < 0 and r3 > 0, "strcmp (eq=0 lt<0 gt>0)", "strcmp (expect eq=0 lt<0 gt>0)")
+
+def test_strncpy():
+    testcheck.section("Test 5: strncpy")
+    buf: t.CChar | t.CPtr = w32.win32memory.VirtualAlloc(None, 64, 12288, 4)
+    if t.CUInt64T(buf) == 0:
+        stdio.printf("SKIP: VirtualAlloc returned NULL\n")
+        return
+    string.memset(buf, 0, 64)
+    string.strncpy(buf, "ABCDEFGHIJ", 5)
+    cmp_result: t.CInt = string.strcmp(buf, "ABCDE")
+    testcheck.check(cmp_result == 0, "strncpy (result=ABCDE)", "strncpy (cmp mismatch)")
+
+def test_char_access():
+    testcheck.section("Test 6: char access")
+    s: t.CChar | t.CPtr = "ABCDE"
+    val: t.CUInt8T = s[2]  # 'C' = 67
+    testcheck.check(val == 67, "char access (s[2]=67='C')", "char access (s[2] expect 67)")
+
+def test_snprintf():
+    testcheck.section("Test 7: snprintf")
+    buf: t.CChar | t.CPtr = w32.win32memory.VirtualAlloc(None, 128, 12288, 4)
+    if t.CUInt64T(buf) == 0:
+        stdio.printf("SKIP: VirtualAlloc returned NULL\n")
+        return
+    string.memset(buf, 0, 128)
+    stdio.snprintf(buf, 128, "value=%d hex=0x%x str=%s", 42, 255, "test")
+    cmp_result: t.CInt = string.strcmp(buf, "value=42 hex=0xff str=test")
+    testcheck.check(cmp_result == 0, "snprintf (result=value=42 hex=0xff str=test)", "snprintf (result mismatch)")
+
+import w32.win32memory
+
+def main() -> t.CInt:
+    testcheck.begin("StringTest: 字符串操作基准测试")
+    test_strlen()
+    test_strcpy()
+    test_strcat()
+    test_strcmp()
+    test_strncpy()
+    test_char_access()
+    test_snprintf()
+    return testcheck.end()