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/Python/strdup.c

@@ -0,0 +1,14 @@
+/* strdup() replacement (from stdwin, if you must know) */
+
+#include "pgenheaders.h"
+
+char *
+strdup(const char *str)
+{
+	if (str != NULL) {
+		register char *copy = malloc(strlen(str) + 1);
+		if (copy != NULL)
+			return strcpy(copy, str);
+	}
+	return NULL;
+}