Add GuestHeap size-classed reuse pool + oversized-allocation free-list

GuestHeap previously bump-allocated any request >64KiB and never
reclaimed it on free() - a real, sustained gameplay session eventually
exhausted the arena (traced live to two separate crashes: onCreate
never completing, and a NULL-vector dereference in sub_4BA588 caused
by a failed ~175KB allocation going unchecked by the real EA code).

Widen the existing O(1) size-class free list (already used for <=64KiB
requests) to cover the whole arena instead of adding a second reuse
mechanism next to it - oversized allocations now pool and reclaim the
same way small ones already did. Add matching desktop tests
(guest_heap_test.cpp, run via run_heap_tests.sh) covering the exact
failing size from the crash log and a sustained alloc/free cycle in an
arena too small to survive without reclaim.

Verified live on device: the crash is gone across a full 10-minute
session with sustained GLES rendering throughout.

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

mpcore/scripts/run_heap_tests.sh

@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+# Desktop-only GuestHeap test harness (see guest_heap_test.cpp's own top
+# comment) - no Android, no Unicorn, no APK, no device. Compiles
+# guest_heap.cpp directly against the host's own C++ compiler and runs the
+# resulting binary. Fast feedback loop for changes to the guest heap
+# allocator before ever touching a device.
+set -euo pipefail
+cd "$(dirname "$0")/.."
+
+SRC_DIR="src/main/cpp/emu"
+OUT="${TMPDIR:-/tmp}/guest_heap_test"
+
+c++ -std=c++17 -O0 -g -Wall \
+    "$SRC_DIR/guest_heap.cpp" \
+    "$SRC_DIR/tests/guest_heap_test.cpp" \
+    -I"$SRC_DIR" \
+    -o "$OUT"
+
+"$OUT"