self-review 2026-05-18: add embed_ok to heartbeat ISE

Ollama availability is a silent failure mode: when the embedding service
is down, semantic seed injection falls back to lexical-only activation with
no signal in the ISE stream. Add embed_ok field (0/1) to every heartbeat
by probing http://localhost:11434 — makes Ollama health visible without
a separate monitoring path.

dist/elp-c-decls.h

@@ -226,6 +226,7 @@ el_val_t elapsed_ms(void);
 el_val_t elp_detect_predicate(el_val_t msg);
 el_val_t elp_extract_topic(el_val_t msg);
 el_val_t elp_parse(el_val_t msg);
+el_val_t embed_ok(void);
 el_val_t emit_heartbeat(void);
 el_val_t emit_session_start_event(void);
 el_val_t en_irregular_plural(el_val_t word);