Give cross-cutting concerns an owner instead of a convention (#145)

lang/runtime/el_runtime.h

@@ -1023,6 +1023,22 @@ el_val_t  __url_decode(el_val_t s);
 /* Environment */
 el_val_t  __env_get(el_val_t key);
 
+/* Cross-cutting concerns declared by a `program` block (spec §18).
+ * All three are COMPILER-INJECTED at the head of main() — they are not meant to
+ * be written by hand, which is the point: the guarantee cannot be forgotten at a
+ * call site because there is no call site. */
+el_val_t  el_singleton_acquire(el_val_t id);                    /* §18.1 process identity */
+el_val_t  el_config_declare(el_val_t name, el_val_t type,
+                            el_val_t deflt, el_val_t has_default,
+                            el_val_t required);                 /* §18.2 config schema    */
+el_val_t  el_config_validate(el_val_t program_name);            /* §18.2 startup validate */
+
+/* config(key) — the READ side, and the only one programs write by hand. With a
+ * schema declared it is a validated lookup; without one it degrades to getenv.
+ * (Defined in el_runtime.c but previously never prototyped here, so any program
+ * calling it failed to compile under -Werror=implicit-function-declaration.) */
+el_val_t  config(el_val_t key);
+
 /* Subprocess */
 el_val_t  __exec(el_val_t cmd);
 el_val_t  __exec_bg(el_val_t cmd);