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>

audit/port-map/EterBase/CRC32.cpp.json

@@ -6,11 +6,11 @@
   "functions": {
     "GetCRC32": {
       "impl": [
-        "extension/src/platform/EterBase/CRC32.cpp:GetCRC32"
+        "src/platform/EterBase/CRC32.cpp:GetCRC32"
       ],
       "status": "ADAPTED",
       "note": "platform CRC32 table implementation; same polynomial and GetCRC32 values (checked against every stored filename_crc)",
-      "test": "extension/tests/port_eterpack_test.cpp (103 packs, 54891 entries, first-registered wins, 4 SECURITY rejects)"
+      "test": "tests/port/port_eterpack_test.cpp (103 packs, 54891 entries, first-registered wins, 4 SECURITY rejects)"
     },
     "GetCaseCRC32": {
       "status": "TODO"