A top-level `asm { "tmpl", };` block (template only) lowers to LLVM `module asm`;
a lib-less `extern` declaration calls into the symbols it defines (the import
direction reuses the existing C-FFI extern path — no new surface).
- ast.zig: asm_global node (AsmGlobal { template }).
- parser.zig: parseAsmGlobal, dispatched from parseTopLevel on kw_asm — rejects
`volatile` and any operands/clobbers (template only). The in-function asm
expression form stays in parsePrimary.
- module.zig: Module.global_asm list; lower/decl.zig captures each template in
lowerMainAndComptime (the real top-level pass — lowerDecls is dead for
top-level); emit_llvm.zig emit() appends each via LLVMAppendModuleInlineAsm in
source order.
- the new node forced asm_global arms in sema.zig (analyzeNode +
findNodeAtOffset) and semantic_diagnostics.zig (checkBindingNames).
Verified end-to-end: an aarch64 `_my_add` global routine, called via `extern`,
returns 42 — AOT only (the ORC JIT doesn't link module-asm symbols; global-asm
symbols live in the final linked binary). Locked with 1648-platform-asm-global
({ "aot": true, "target": "macos" } → AOT build+run on aarch64, ir-only else).
zig build test green (656 corpus, 446 unit).
