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/sleep.c

@@ -0,0 +1,41 @@
+#include "oslib/osmodule.h"
+#include <stdio.h>
+#include "kernel.h"
+#include <limits.h>
+#include <errno.h>
+#include "oslib/taskwindow.h"
+#include "Python.h"
+
+
+int riscos_sleep(double delay)
+{
+    os_t starttime, endtime, time; /* monotonic times (centiseconds) */
+    int *pollword, ret;
+    osbool claimed;
+
+    /* calculate end time */
+    starttime = os_read_monotonic_time();
+    if (starttime + 100.0*delay >INT_MAX)
+        endtime = INT_MAX;
+    else
+        endtime = (os_t)(starttime + 100.0*delay);
+
+    /* allocate (in RMA) and set pollword for xupcall_sleep */
+    pollword = osmodule_alloc(4);
+    *pollword = 1;
+
+    time = starttime;
+    ret = 0;
+    while ( time<endtime && time>=starttime ) {
+        xupcall_sleep (pollword, &claimed);
+        if (PyErr_CheckSignals()) {
+            ret = 1;
+            break;
+        }
+        time = os_read_monotonic_time();
+    }
+
+    /* deallocate pollword */
+    osmodule_free(pollword);
+    return ret;
+}