port(2P step 3a/3b): stdlib on sys.path + the pack module

step 3a — 标准库:
  tools/py_embed/make_stdlib_zip.py packs the vendored Lib/ into
  <build>/python27.zip (397 modules, 6876547 bytes, ZIP_STORED — the zlib
  module is trimmed out of our CPython, so zipimport cannot inflate).
  The mtpython_stdlib target builds it; py_embed_test and the launcher test
  both run against it.
  platform/ScriptLib/PythonHost sets the embedding flags before
  Py_Initialize and, after it, puts the zip on sys.path and re-registers
  encodings.search_function with codecs — 2.7 builds the codec registry
  once, at startup, so replacing sys.path afterwards needs it back.

step 3b — pack 模块:
  UserInterface/PythonPackModule.cpp copied verbatim; packExist/packGet/
  initpack read root/ and uiscript/ through CEterPackManager, i.e. through
  asset_io. The CHINA_CRYPT_KEY block in that unit is CAccountConnector's
  and is kept #if 0 until the login slice (2V1). UserInterface/StdAfx.h is
  a documented partial mirror — the original is the whole client's PCH.

The launcher test now runs initpack() as RunMainScript does (its first
line), reads system.py / uiscript / locale text back out of the packs, and
confirms cp1252 decoding works off the zip. system.py still stops at
"No module named app" — the C++ modules are the 2V0 slice.

gates: port_map.py check 0 errors · key leak check 8/8 none · macOS ctest
27/27 · android + ios port_platform compile clean.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tools/py_embed/make_stdlib_zip.py

@@ -0,0 +1,59 @@
+#!/usr/bin/env python3
+"""Pack the vendored CPython 2.7.18 Lib/ into the python27.zip the host puts on sys.path.
+
+  make_stdlib_zip.py <Lib dir> <out.zip>
+
+40250 shipped a real python27 installation, so `import encodings` found Lib/ through the
+interpreter's prefix. The embedded interpreter has no prefix (Py_FrozenFlag, no site), so the host
+supplies the stdlib as this one file — the arrangement validated on the device by
+tools/py_embed_android/build-and-run.sh (PORT-PLAN 批次 2P step 3).
+
+Entries are STORED, never deflated: the zlib module is not in the vendored Modules/ (see
+docs/THIRD-PARTY.md), so zipimport could not inflate them. Only .py goes in; zipimport reads
+source as happily as bytecode, and .pyc would pin the magic number to the build host's interpreter.
+Written deterministically (sorted, fixed timestamp) so the file's sha256 identifies its contents —
+3c checks that hash when staging the zip into a mobile sandbox.
+"""
+
+from __future__ import annotations
+
+import sys
+import zipfile
+from pathlib import Path
+
+# Test suites, the Tk/2to3/bsddb/pip trees and the platform-specific stubs: none of the 40250 scripts
+# or their imports reach them, and they are most of the size.
+SKIP_DIRS = {"test", "tests", "lib-tk", "idlelib", "lib2to3", "bsddb", "ensurepip", "curses",
+             "distutils", "unittest", "wsgiref", "multiprocessing", "compiler"}
+
+
+def main() -> int:
+    if len(sys.argv) != 3:
+        print(__doc__, file=sys.stderr)
+        return 2
+    lib, out = Path(sys.argv[1]), Path(sys.argv[2])
+    if not (lib / "os.py").is_file():
+        print(f"make_stdlib_zip: {lib} is not a CPython Lib/ directory", file=sys.stderr)
+        return 1
+
+    members = []
+    for path in sorted(lib.rglob("*.py")):
+        rel = path.relative_to(lib)
+        if rel.parts[0].startswith("plat-") or SKIP_DIRS.intersection(rel.parts[:-1]):
+            continue
+        members.append((rel, path))
+
+    out.parent.mkdir(parents=True, exist_ok=True)
+    tmp = out.with_suffix(".zip.tmp")
+    with zipfile.ZipFile(tmp, "w", zipfile.ZIP_STORED) as zf:
+        for rel, path in members:
+            info = zipfile.ZipInfo(rel.as_posix(), date_time=(1980, 1, 1, 0, 0, 0))
+            info.external_attr = 0o644 << 16
+            zf.writestr(info, path.read_bytes())
+    tmp.replace(out)
+    print(f"make_stdlib_zip: {out} ({len(members)} modules, {out.stat().st_size} bytes)")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())