refactor(ffi-linkage): Phase 9.3 — purge 'foreign' from comments (src caps + examples + docs)

src/: ~21 capital-Foreign comments the case-sensitive verify grep missed
(Foreign-class→Runtime-class, Foreign path→Runtime path, Foreign decls→Extern decls,
FOREIGN function→extern function) across calls/inst/ffi_objc/jni_descriptor/emit_llvm/
c_import/lower.*/ops. src 'foreign' now = ONLY the hash_foreign token + 4 rejection
messages (9.0-delete targets). examples/*.sx comments → extern/runtime-class (1219
stdout regen; KEPT 1176). docs/inline-asm-design + debugger purged. Comments only —
no build impact. 9.0 ratified: DELETE hash_foreign token next.

src/ir/emit_llvm.zig

@@ -2250,7 +2250,7 @@ pub const LLVMEmitter = struct {
 
     /// Coerce a call argument to match the expected parameter type.
     /// Handles int width mismatches (trunc/ext), float width, and int↔float.
-    /// How a FOREIGN function's declared sx return maps onto a C `char *`:
+    /// How an EXTERN function's declared sx return maps onto a C `char *`:
     /// `-> string` (.plain) and `-> ?string` (.optional) both receive one
     /// pointer from C; everything else is `.none`. Keep `declareFunction`'s
     /// signature building and `emitCall`'s result synthesis keyed on the