fix(verify): fix non-amd64 JIT trampolines and validate under qemu

docs/DECISIONS.md

@@ -35,8 +35,24 @@ for the lifetime of the GOOBJ emission.
 
 ## 2026-08-30 non-amd64 JIT execution trampolines
 
-**Status:** open (blocks runtime verification on arm64, riscv64 and
-loong64 hosts).
+**Status:** resolved for riscv64 (validated end to end under qemu-user)
+and arm64 (fix in place, consistent with the observed frame convention);
+open for loong64 until hardware validation.
+
+**Root cause (found 2026-08-31).**  The trampolines advanced SP past the
+leave-address slot after loading it, while the assembled kernels read
+their first argument at SP+8 per the frame convention (the amd64 path
+already kept SP on that slot).  Removing the advance fixed riscv64
+immediately (plain and checked ABI tests pass under qemu-user); the
+arm64 kernel's pre-fix trace showed exactly the same SP+8 reading.  The
+apparent arm64/loong64 "crashes in the JIT" turned out to be dominated
+by an unrelated instability: the Go 1.26 and 1.27 runtimes crash under
+qemu-user arm64 emulation (GC worker start, identical signature with the
+JIT tests skipped, both qemu 7.2 and 10.2), and the Go loong64 runtime
+does not start at all.  `gasm verify` therefore keeps loong64 kernels on
+the ground-truth path until hardware validation; the GOARCH-guarded
+tests (`verify/jit_arch_test.go`, `verify/abi_arch_test.go`) are the
+hardware validation entry point.
 
 **State.**  The per-architecture trampolines compile for all targets, the
 kernels they execute are byte-for-byte correct against `go tool asm`, and