layout: restructure into src/ tests/ android/ scripts/ tools/

- extension/src/{port,platform,codepage} -> src/; native_render -> src/host
  (+ dxt, shaders/); libgr2 -> src/gr2; extension/third_party -> third_party
- extension/tests -> tests/port, libgr2/tests -> tests/gr2
- android-native -> android (build.sh, push-client.sh moved in)
- script -> scripts; tools/40250 -> tools/server; oracle -> tools/granny-oracle;
  perf tools -> tools/perf
- all build trees under build/ (native, release, android, port-gate)
- xrender:: CMake aliases -> mt::; port-map ledger impl paths rewritten

No code changes. ctest 15/15, port_gate macos+android PASS, port_map check 0 errors.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

third_party/cpython-2.7.18/RISCOS/Modules/getpath_riscos.c

@@ -0,0 +1,60 @@
+#include "Python.h"
+#include "osdefs.h"
+
+static char *prefix, *exec_prefix, *progpath, *module_search_path=NULL;
+
+static void
+calculate_path()
+{
+    char *pypath = getenv("Python$Path");
+    if (pypath) {
+        int pathlen = strlen(pypath);
+        module_search_path = malloc(pathlen + 1);
+        if (module_search_path)
+            strncpy(module_search_path, pypath, pathlen + 1);
+        else {
+            fprintf(stderr,
+                "Not enough memory for dynamic PYTHONPATH.\n"
+                "Using default static PYTHONPATH.\n");
+        }
+    }
+    if (!module_search_path)
+        module_search_path = "<Python$Dir>.Lib";
+    prefix = "<Python$Dir>";
+    exec_prefix = prefix;
+    progpath = Py_GetProgramName();
+}
+
+/* External interface */
+
+char *
+Py_GetPath()
+{
+    if (!module_search_path)
+        calculate_path();
+    return module_search_path;
+}
+
+char *
+Py_GetPrefix()
+{
+    if (!module_search_path)
+        calculate_path();
+    return prefix;
+}
+
+char *
+Py_GetExecPrefix()
+{
+    if (!module_search_path)
+        calculate_path();
+    return exec_prefix;
+}
+
+char *
+Py_GetProgramFullPath()
+{
+    if (!module_search_path)
+        calculate_path();
+    return progpath;
+}