seam refusal + control tests: a runtime binding can short-circuit

Prediction 3 was FALSE. I expected refusal to be impossible through the seam
because the entry indirection discarded its return. One line:

    { el_val_t __s = el_seam_run(EL_STR(f), 0, 0); if (__s) return __s; }

work() returns 7; bound to a refusing construct AFTER the build it returns 42.
So three of the five compile-time kinds are runtime-bindable: entry injection,
exit injection, and refusal. wraps_body needs invocation control and
prohibits_outside is compile-time by nature.

104/104 native compiler tests pass.

lang/tests/native/test_compiler.el

@@ -903,3 +903,24 @@ test "seeded-vbd-prohibition-still-enforced" {
     let out: String = compile_capture(src)
     assert str_contains(out, "may only be called from an @manager fn"), "the compiled-in core prohibition survives being declared rather than branched"
 }
+
+// ── Runtime seam ─────────────────────────────────────────────────────────────
+//
+// CONTROL for the finding that a crossing can be resolved at execution rather
+// than at emission. Codegen emits one unconditional indirection per fn; which
+// constructs apply is read from a table written after the binary exists.
+
+test "seam-indirection-emitted-on-every-fn" {
+    let src: String = "fn a() -> Int { return 1 }\nfn b() -> Int { return 2 }"
+    let out: String = compile_capture(src)
+    assert str_contains(out, "el_seam_run(EL_STR(\"a\"), 0, 0);"), "fn a carries the indirection"
+    assert str_contains(out, "el_seam_run(EL_STR(\"b\"), 0, 0);"), "fn b carries the indirection"
+}
+
+test "seam-emitted-without-any-decorator" {
+    // The point of the seam: source need not mention a construct at all.
+    let src: String = "fn undecorated() -> Int { return 1 }"
+    let out: String = compile_capture(src)
+    assert str_contains(out, "el_seam_run"), "an undecorated fn is still bindable at runtime"
+    assert !str_contains(out, "engram_boundary_beat"), "and nothing is inlined for it"
+}