fix: Add framebuffer release/realloc and improved lazy indexing (#2563)

lib/Memory/BuildScratch.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <cstddef>
+#include <cstdint>
+
+// Registry for the framebuffer bytes lent out during a build phase
+// (GfxRenderer::FrameBufferLoan). The lender (GfxRenderer) deposits the block
+// with lend()/reclaim(); a memory-hungry consumer (e.g. InflateStream's ~43KB
+// tinfl state + window) may claim() it instead of allocating from the heap.
+//
+// Exactly one claimant at a time; claim() returns nullptr when the block is
+// absent or already claimed, and consumers must fall back to the heap. The
+// underlying storage is the framebuffer allocation itself, which is never
+// freed -- so even the pathological case (reclaim() while still claimed, which
+// logs an error) reads garbage, never freed memory.
+namespace buildscratch {
+
+// Lender side (GfxRenderer only).
+void lend(uint8_t* buf, size_t len);
+void reclaim();
+
+// Consumer side: exclusive claim of the whole block if it is at least minLen
+// bytes; nullptr means "use the heap". Release with the same pointer.
+uint8_t* claim(size_t minLen, size_t* lenOut = nullptr);
+void release(const uint8_t* p);
+
+}  // namespace buildscratch