fix(el-runtime): promote http_handler typedefs to el_runtime.h (cross-module + Windows)

http_handler_fn / http_handler4_fn were defined only inside el_runtime.c, so soul
modules (routes/chat/...) that reference them via cross-module forward declarations
couldn't see the types — which broke the Windows link of every module. Moving the
public function-pointer types to the shared header is the correct home and unblocks
the build on all platforms (identical typedef, C11-safe redefinition in el_runtime.c).

With this, the soul links into a native Windows neuron.exe (mingw, static) that boots
and serves HTTP on :7770 — verified /health → 200 {"status":"alive",...} in a Win11 VM.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lang/el-compiler/runtime/el_runtime.h

@@ -52,6 +52,12 @@
 
 typedef int64_t el_val_t;
 
+/* HTTP request-handler function-pointer types. Public because soul modules (routes/chat/etc.)
+ * register handlers across translation units; previously defined only inside el_runtime.c, which
+ * made cross-module references (and the Windows build) fail. Home in the shared header. */
+typedef el_val_t (*http_handler_fn)(el_val_t method, el_val_t path, el_val_t body);
+typedef el_val_t (*http_handler4_fn)(el_val_t method, el_val_t path, el_val_t body, el_val_t headers);
+
 #define EL_STR(s)  ((el_val_t)(uintptr_t)(s))
 #define EL_CSTR(v) ((const char*)(uintptr_t)(v))
 #define EL_INT(v)  (v)