wcc: cgdot/cgident dead-end paths are loud (rule 7)

cgdot's local-ident arm silently emitted nothing for a receiver
whose local record carries no type node (inference miss upstream),
leaving the consumer reading stale AX. cgident's tail silently
emitted nothing for any ident that resolved to no local/fn/def/let;
that silence is load-bearing ONLY for the #140 !void error-singleton
value (tag-only, the widen arm stamps the tag) -- keep exactly that
case, mirroring the cstage #140 guard, and hard-stop the rest.

selfhost/cmd/wcc/cgenexpr.ww

@@ -1388,7 +1388,19 @@ fn cgident(c: *cgen, n: *syntax.node) void = {
 		};
 		return;
 	};
-	return;
+	// #140: a `!void` error-singleton spelled as a VALUE (`return
+	// toolong;`) is tag-only — the void payload has size 0 and no
+	// storage, so it is neither a local, def, nor let. Emit NOTHING;
+	// the enclosing widen arm stamps the variant tag. Mirrors cstage
+	// cgen.c N_IDENT #140 guard. Every other unresolvable ident is
+	// checker-rejected upstream — loud, never the old silent return.
+	{
+		let vu: *syntax.tinfo = tichase(n.type_: *syntax.tinfo);
+		if (vu != nil && vu.kind == syntax.tykind.TY_VOID) { return; };
+	};
+	let mur: str = "cgident: unresolvable identifier (rule 7)\n";
+	os.write(2, mur.ptr, mur.len: u64);
+	os.exit(1);
 };
 
 // cgslicehdr — load the 24B slice/str header at base+0 into the
@@ -3707,7 +3719,16 @@ fn cgdot(c: *cgen, n: *syntax.node) void = {
 					};
 					tn = nx;
 				};
-				if (tn == nil) { return; };
+				// A registered local with NO type node means
+				// inference missed upstream — emitting nothing
+				// leaves the consumer reading stale AX, and
+				// falling through would emit a bogus
+				// `MOVQ <fld>(SB)` (the #191 hazard). Loud.
+				if (tn == nil) {
+					let mdt: str = "cgdot: local receiver has no type node (rule 7)\n";
+					os.write(2, mdt.ptr, mdt.len: u64);
+					os.exit(1);
+				};
 				let lkind: syntax.nkind = tn.kind;
 				// Pointer-to-struct: deref then field load.
 				if (lkind == syntax.nkind.N_TPTR) {