lang: declare the el_runtime.c symbols el_seed.c's wrappers call

runtime/el_seed.c does not compile standalone via the exact command
tools/install.sh uses (`cc -std=c11 -O2 -I runtime -c runtime/el_seed.c`):
51 of its __-prefixed wrapper functions (http serving, JSON access, key-val
state, URL/HTML escaping, and the whole engram_* node/edge/layer/search
surface) call unprefixed counterparts that are implemented in el_runtime.c,
not in el_seed.c itself, and el_seed.c never declared them -- a toolchain
that treats an implicit function declaration as a hard error under C11
fails the compile outright.

install.sh already compiles el_seed.c and el_runtime.c as separate objects
and archives both into libel.a, so the symbols are always present at link
time; el_seed.c alone was just missing the prototypes.

A plain `#include "el_runtime.h"` was tried first and rejected: it redefines
el_to_float/el_from_float, which el_seed.h already provides -- a real
compile error, not a style preference. Added narrow prototypes instead,
copied verbatim from el_runtime.h, for exactly the 51 symbols el_seed.c's
wrappers reference and nothing else.

Verified clean:
  - `cc -std=c11 -O2 -I runtime -c runtime/el_seed.c` (install.sh's exact
    per-file compile) -- 0 errors, 0 warnings, even with -ferror-limit=0.
  - full `tools/install.sh` run -- compiles both objects and archives them
    into libel.a successfully.

Separately (not fixed here, out of scope): AGENTS.md's documented compiler
self-rebuild command links elc-new.c against el_seed.c, but elc-new.c's own
generated `#include "el_runtime.h"` line and 3 undeclared symbols
(el_mem_check, stdout_to_file, stdout_restore -- present in neither
el_runtime.c nor el_seed.c) mean that command fails regardless of which
runtime file it's linked against; and install.sh's libel.a only archives
el_seed.o + el_runtime.o, so any program that calls into the engram_*
surface fails to link against it (el_runtime.c's engram_* wrappers need
engram_store.c/engram_geometry.c/engram_reason.c/engram_cognition.c/
engram_vindex.c, none of which install.sh compiles in). Both are real,
pre-existing, and independent of this fix -- worth their own look.

lang/runtime/el_seed.c

@@ -37,6 +37,82 @@
 #include <dlfcn.h>
 #include <curl/curl.h>
 
+/* el_runtime.c bridge prototypes.
+ *
+ * A block of __-prefixed wrappers further down in this file (http serving,
+ * JSON access, key-val state, URL/HTML escaping, and the whole engram_*
+ * node/edge/layer/search surface -- 51 symbols in total) delegate to
+ * unprefixed counterparts that are implemented in el_runtime.c, not here.
+ * Porting them into native el_seed.c or El has not happened yet.
+ * tools/install.sh compiles el_seed.c and el_runtime.c as separate objects
+ * and archives both into libel.a, so the symbols are always present at link
+ * time. el_seed.c alone was just missing the prototypes, which made even a
+ * standalone -c compile of this one file fail on a toolchain that now treats
+ * an implicit function declaration as a hard error under C11.
+ *
+ * A plain include of el_runtime.h was tried first and rejected: it redefines
+ * el_to_float and el_from_float, which el_seed.h already provides. Narrow
+ * prototypes, copied verbatim from el_runtime.h, avoid that collision without
+ * pulling in the rest of the retiring runtime header.
+ */
+el_val_t http_response(el_val_t status, el_val_t headers_json, el_val_t body);
+void     http_serve(el_val_t port, el_val_t handler);
+void     http_serve_v2(el_val_t port, el_val_t handler);
+el_val_t json_get(el_val_t json, el_val_t key);
+el_val_t json_get_string(el_val_t json_str, el_val_t key);
+el_val_t json_get_int(el_val_t json_str, el_val_t key);
+el_val_t json_get_float(el_val_t json_str, el_val_t key);
+el_val_t json_get_bool(el_val_t json_str, el_val_t key);
+el_val_t json_get_raw(el_val_t json_str, el_val_t key);
+el_val_t json_parse(el_val_t s);
+el_val_t json_set(el_val_t json_str, el_val_t key, el_val_t value);
+el_val_t json_stringify(el_val_t v);
+el_val_t json_array_len(el_val_t json_str);
+el_val_t json_array_get(el_val_t json_str, el_val_t index);
+el_val_t json_array_get_string(el_val_t json_str, el_val_t index);
+el_val_t state_set(el_val_t key, el_val_t value);
+el_val_t state_get(el_val_t key);
+el_val_t state_del(el_val_t key);
+el_val_t state_keys(void);
+el_val_t url_encode(el_val_t s);
+el_val_t url_decode(el_val_t s);
+el_val_t el_html_sanitize(el_val_t input_html, el_val_t allowlist_json);
+el_val_t engram_node(el_val_t content, el_val_t node_type, el_val_t salience);
+el_val_t engram_node_full(el_val_t content, el_val_t node_type, el_val_t label,
+                           el_val_t salience, el_val_t importance, el_val_t confidence,
+                           el_val_t tier, el_val_t tags);
+el_val_t engram_node_layered(el_val_t content, el_val_t node_type, el_val_t label,
+                              el_val_t salience, el_val_t certainty, el_val_t confidence,
+                              el_val_t status, el_val_t tags, el_val_t layer_id);
+el_val_t engram_add_layer(el_val_t name, el_val_t priority, el_val_t suppressible,
+                           el_val_t transparent, el_val_t injectable);
+el_val_t engram_remove_layer(el_val_t layer_id);
+el_val_t engram_list_layers(void);
+el_val_t engram_list_layers_json(void);
+el_val_t engram_get_node(el_val_t id);
+el_val_t engram_get_node_json(el_val_t id);
+el_val_t engram_get_node_by_label(el_val_t label);
+void     engram_strengthen(el_val_t node_id);
+void     engram_forget(el_val_t node_id);
+el_val_t engram_node_count(void);
+el_val_t engram_edge_count(void);
+el_val_t engram_scan_nodes(el_val_t limit, el_val_t offset);
+el_val_t engram_scan_nodes_json(el_val_t limit, el_val_t offset);
+el_val_t engram_scan_nodes_by_type_json(el_val_t node_type, el_val_t limit, el_val_t offset);
+el_val_t engram_search(el_val_t query, el_val_t limit);
+el_val_t engram_search_json(el_val_t query, el_val_t limit);
+el_val_t engram_activate(el_val_t query, el_val_t depth);
+el_val_t engram_activate_json(el_val_t query, el_val_t depth);
+el_val_t engram_compile_layered_json(el_val_t intent, el_val_t depth);
+el_val_t engram_stats_json(void);
+void     engram_connect(el_val_t from_id, el_val_t to_id, el_val_t weight, el_val_t relation);
+el_val_t engram_edge_between(el_val_t from_id, el_val_t to_id);
+el_val_t engram_neighbors(el_val_t node_id);
+el_val_t engram_neighbors_filtered(el_val_t node_id, el_val_t max_depth, el_val_t direction);
+el_val_t engram_neighbors_json(el_val_t node_id, el_val_t max_depth, el_val_t direction);
+el_val_t engram_load(el_val_t path);
+el_val_t engram_save(el_val_t path);
+
 /* ── Private allocator ───────────────────────────────────────────────────── */
 /*
  * el_seed.c carries its own arena for per-request allocation tracking.