runtime: add dharma-required functions to el_runtime.c and runtime/*.el

Add the following functions that dharma registry calls but were missing
from the El runtime:

el_runtime.c (consumed by the old build system via released SDK):
  - list_len, list_get — aliases for el_list_len/el_list_get (handlers.el)
  - json_array_push — append pre-encoded element to JSON array string
  - now_millis, unix_timestamp_ms, time_now_ms — ms-since-epoch aliases
  - log_info, log_warn — structured stderr log helpers
  - config — reads config from environment (alias for getenv)
  - http_patch — HTTP PATCH with Content-Type: application/json
  - http_post_engram — HTTP POST with optional X-API-Key header
  - http_get_engram — HTTP GET with optional X-API-Key header
  - str_to_bytes — encode string as JSON byte array [72,101,...]
  - bytes_to_str — decode JSON byte array back to string
  - hash_sha256 — SHA-256 hex digest using built-in sha256 impl

runtime/*.el (consumed by the new build system):
  - http.el: http_patch, http_post_engram, http_get_engram
  - time.el: now_millis, unix_timestamp_ms, time_now_ms
  - env.el: config, log_info, log_warn, list_len, list_get
  - json.el: json_array_push, bytes_to_str
  - string.el: str_to_bytes, hash_sha256 (via __sha256_hex seed)

el_seed.h / el_seed.c:
  - __sha256_hex primitive with self-contained SHA-256 implementation

runtime/time.el

@@ -400,3 +400,26 @@ fn uuid_new() -> String {
 fn uuid_v4() -> String {
     return __uuid_v4()
 }
+
+// ---------------------------------------------------------------------------
+// DHARMA-compatible aliases — millisecond-precision timestamps.
+//
+// now_millis, unix_timestamp_ms, and time_now_ms all return the same value:
+// milliseconds since the Unix epoch. They exist because different parts of
+// the dharma codebase use different names for the same concept.
+// ---------------------------------------------------------------------------
+
+// now_millis — milliseconds since Unix epoch. Alias for time_now().
+fn now_millis() -> Int {
+    return __time_now_ns() / 1000000
+}
+
+// unix_timestamp_ms — same as now_millis.
+fn unix_timestamp_ms() -> Int {
+    return __time_now_ns() / 1000000
+}
+
+// time_now_ms — same as now_millis.
+fn time_now_ms() -> Int {
+    return __time_now_ns() / 1000000
+}