feat(binary-layout): admit ELF64 AArch64 and name the refused host (#8711)

* feat(binary-layout): admit ELF64 AArch64 and name the refused host

inspect_binary_layout refused every AArch64 ELF, and on a non-x64 host the
refusal read "supports Linux x64 only", which looked like a target refusal
(#8709 ran on arm64 WSL and suspected an e_machine check).

The pwntools adapter now admits little-endian ELF64 AArch64 EXEC/DYN/REL
objects alongside the existing profiles, pwntools must report aarch64/64/
little, and the Evidence subject names arm64. The host refusal now names the
detected platform/arch and says the target was not read; the host check
itself is unchanged.

verify:binary:layout cross-compiles an AArch64 executable and relocatable
object (never executed) and checks sections, symbols and relocations
against GNU readelf, decoding ELF64 r_info as a 32-bit type under a 32-bit
symbol index. The real-binary-layout workflow installs the toolchain.

Refs #8709

* test(binary-layout): refuse RISC-V as the unsupported machine and assert the host refusal path

verify:binary:layout used e_machine 183 (AArch64) as its unsupported
target, which this branch now admits; use EM_RISCV (243) instead.

The unsupported-host provider test now asserts the refusal names this
host's platform/arch and says the target was not read, so reverting the
decoder to the old message fails it.

src/application/binaryDiagnostics/BinaryLayoutService.test.ts

@@ -58,6 +58,7 @@ it("records the decoded layout once in its Evidence", async () => {
 
 it.each([
   [{ machine: "EM_X86_64", bits: 64, byte_order: "little" }, "x86_64"],
+  [{ machine: "EM_AARCH64", bits: 64, byte_order: "little" }, "arm64"],
   [{ machine: "EM_386", bits: 32, byte_order: "little" }, "x86"],
   [{ machine: "EM_ARM", bits: 32, byte_order: "little" }, "arm"],
   [{ machine: "EM_MIPS", bits: 32, byte_order: "big" }, "mips"],