engram: fix silently-wrong query params, and make el_seed.o + el_runtime.o link

Three real bugs, all found by actually running the thing rather than reading it.

1. query_param never URL-decoded. A GET of /api/search?q=neural%20network
   searched for the literal string "neural%20network" and returned []. Every
   multi-word search against the live engram has been silently returning empty
   results — not an error, an empty result, which is why it went unnoticed.
   Affects every GET route that reads query params, not just search.

2. query_param matched key names unanchored. str_index_of(qs, "q=") matches
   inside "faq=", so "?faq=X&q=Y" returned X for key "q". Verified live before
   the fix. Now searches for "&key=" against "&"+querystring so a match can
   only land on a real parameter boundary.

3. el_request_start/el_request_end were defined in BOTH el_seed.c and
   el_runtime.c, so linking the two objects together — which is exactly what
   the product build does — failed with duplicate symbols. el_seed.c's own
   comment already says these moved there ("formerly defined in el_runtime.c.
   Now self-contained in el_seed.c"); the el_runtime.c copies were left behind
   during that move. Removed them, kept declarations since http_worker calls
   them. Also added the three missing prototypes (engram_op_assert_json,
   engram_node_full_in, engram_connect_in) that el_seed.c wraps but never
   declared, which made it fail to compile standalone under C99+.

Verified: engram builds and links clean from canonical source; before/after
comparison on a copy of the real store shows "neural network" returning a real
match where the live build returns [], and "?faq=WRONG&q=MetaColloc" now
resolving to MetaColloc. Live engram on :8742 was never touched.

lang/runtime/el_seed.c

@@ -1383,6 +1383,17 @@ el_val_t __engram_activate_json(el_val_t query, el_val_t depth) {
     return engram_activate_json(query, depth);
 }
 
+/* Forward decls for el_runtime.c symbols this file wraps. el_seed.c does not
+ * include el_runtime.h (documented in lang/AGENTS.md), so each wrapped symbol
+ * needs a prototype here or clang treats it as an implicit declaration (error
+ * under C99+) and the ABI mis-truncates the el_val_t return. */
+el_val_t engram_op_assert_json(el_val_t node_id, el_val_t depth);
+el_val_t engram_node_full_in(el_val_t purview, 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);
+void     engram_connect_in(el_val_t purview, el_val_t from_id, el_val_t to_id,
+                           el_val_t weight, el_val_t relation);
+
 el_val_t __engram_stats_json(void)                         { return engram_stats_json(); }
 el_val_t __engram_op_assert_json(el_val_t node_id, el_val_t depth) { return engram_op_assert_json(node_id, depth); }
 el_val_t __engram_node_full_in(el_val_t purview, el_val_t content, el_val_t node_type, el_val_t label,