port(2P step 3c): stage python27.zip into the mobile sandbox

CPython opens the stdlib zip with its own stdio, so it needs a real path.
On the desktop res:// is a directory and globalize_path() is enough; in an
exported build res:// is inside the PCK, which nothing outside Godot reads.

  make_stdlib_zip.py now also writes <out>.sha256
  mtpython_stdlib_project copies python27.zip + .sha256 into project/
    (gitignored), and both export presets' include_filter lists them, so
    they enter the PCK — checked with --export-pack
  extension/src/python_stdlib.{h,cpp} (Metin2Python.stdlib_path in
    GDScript): reads the bytes out of the PCK, writes
    user://python27.zip.part, hashes the file as written against the
    shipped digest, then renames. A sandbox copy is reused only when it
    matches, so a first start killed mid-copy and a zip replaced by a new
    build both re-stage instead of feeding zipimport a torn file.
  PythonHost::SetDefaultStdLibPath / DefaultStdLibPath() answer with that
    path ($MT_PYTHON_STDLIB still wins). python_stdlib.cpp is the only unit
    that knows res:// / user://; port_platform stays godot-free.

Also fixes the Windows gate, which step 3b broke: without mtpython the
MinGW build compiled UserInterface/StdAfx.h (it includes ScriptLib/StdAfx.h,
as the original PCH does). port/CMakeLists.txt excludes that header and
PythonPackModule.cpp with ScriptLib, and platform/CMakeLists.txt excludes
platform/ScriptLib/ the same way.

Not done: on-device staging. The macOS test drives the mobile path with
force_stage=true, and nothing in the app boot calls it yet — the
interpreter only starts in the process with 2V0.

gates: python_stdlib_test.gd PASS (in-place path, staging, sha256, bytes
equal res://, no .part, ZIPReader finds encodings/__init__.py, no re-copy
on a second call, corrupted copy re-staged) · macOS ctest 27/27 ·
mingw + android + ios port_platform compile clean · port_map.py check 0
errors · key leak check 8/8 none.

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

extension/src/platform/ScriptLib/PythonHost.cpp

@@ -94,13 +94,24 @@ bool InstallStdLib(const char* stdlib_path, std::string* error)
 	return true;
 }
 
+namespace
+{
+std::string g_staged_path;
+}
+
+void SetDefaultStdLibPath(const char* stdlib_path)
+{
+	g_staged_path = stdlib_path ? stdlib_path : "";
+}
+
 std::string DefaultStdLibPath()
 {
+	// The environment still wins, so a developer can point a build at another stdlib without rebuilding.
 	if (const char* env = getenv("MT_PYTHON_STDLIB"))
 		return env;
-	// Step 3c stages python27.zip out of the packed assets on Android/iOS and answers here; until then
-	// the caller passes the path (the build tree's copy, for the native tests).
-	return "";
+	// Whatever staged the zip for this platform (extension/src/python_stdlib.cpp inside Godot; nothing
+	// in the native tests, which pass the build tree's copy on the command line).
+	return g_staged_path;
 }
 
 }

extension/src/platform/ScriptLib/PythonHost.h

@@ -20,8 +20,9 @@ void Configure(const char* program_name = "eter.python");
 // and re-registers the codec search function. False leaves *error set.
 bool InstallStdLib(const char* stdlib_path, std::string* error);
 
-// The stdlib path this build was given: $MT_PYTHON_STDLIB when set, else the python27.zip next to
-// the executable, else "". Mobile staging (copy out of the app resources, checked against the
-// manifest sha256) is 批次 2P step 3c and will answer here too.
+// Where the host put the stdlib: $MT_PYTHON_STDLIB when set, else whatever SetDefaultStdLibPath was
+// given, else "". Inside Godot that is the staged python27.zip (extension/src/python_stdlib.h), which
+// on Android/iOS is the sandbox copy of the one in the read-only bundle.
 std::string DefaultStdLibPath();
+void SetDefaultStdLibPath(const char* stdlib_path);
 }