feat: the remaining six event types get their parameter forms

MT call, Call connected, Call disconnected, Browser termination, (I-)WLAN
access status and CSG cell selection no longer fall back to the generic
"send a bare notification" prompt:

- MT call (TS 31.111 7.5.1A.2): transaction identifier, calling party number
  + TON -> Address (EFADN BCD coding, encBcdDigits/eventAddressTlv),
  subaddress, IMS URI, media type; source network.
- Call connected (7.5.2A.2) / Call disconnected (7.5.3A.2): transaction
  identifier, near/far-end source select, media type, and a cause - absent,
  the zero-length radio-link-timeout form or custom bytes (the hex field shows
  only for "custom").
- Browser termination (TS 102 223 7.5.9.2): user / error cause.
- (I-)WLAN access status (TS 31.111 7.5.1.2): no coverage / coverage /
  connection on-going.
- CSG cell selection (TS 31.111 7.5.3.2): status + selection mechanism,
  optional access technology, CSG ID, HNB name and PLMN ID; source network.

The device-identities source (TS 102 223 8.7: 82 terminal / 83 network) is now
selectable: EVENT_FORMS carries a fixed `src` or a `srcField`, and
_send_event_download()/`/api/event-send` take an `event_src` override (an
invalid value falls back to the terminal).

Tests: the BCD/Address builders, each event's build vectors, the "no not_yet
left" guard and the server source override.  Help EN/RU, both AGENTS files;
sw cache simple-v348.

pysim_simple_server/server.py

@@ -4276,12 +4276,20 @@ def _verify_adm(scc, app, adm_hex):
             'error': 'Security status not satisfied' if sw == '6982' else 'Error'}
 
 
-def _send_event_download(scc, event_type, event_data=None, drain=True):
+def _send_event_download(scc, event_type, event_data=None, drain=True, src=None):
     """Send ENVELOPE(Event Download) for the given event type.
-    Builds: CLA C2 0000 Lc  D6 [len] (99 01 [type] 82 02 82 81 [extra])"""
+    Builds: CLA C2 0000 Lc  D6 [len] (99 01 [type] 82 02 <src> 81 [extra]).
+    `src` is the source device identity (TS 102 223 8.7: '82' terminal,
+    '83' network); the default is the terminal."""
+    src_byte = 0x82
+    if src:
+        try:
+            src_byte = int(str(src), 16) & 0xFF
+        except (TypeError, ValueError):
+            src_byte = 0x82
     inner = bytearray()
     inner.extend([0x99, 0x01, event_type])
-    inner.extend([0x82, 0x02, 0x82, 0x81])
+    inner.extend([0x82, 0x02, src_byte, 0x81])
     if event_data:
         inner.extend(event_data)
     if len(inner) < 0x80:
@@ -6849,8 +6857,9 @@ class PysimHandler(BaseHTTPRequestHandler):
                 self._send_json({'error': 'event_type is required'}, 400)
                 return
             event_data = bytes.fromhex(event_data_hex) if event_data_hex else None
+            event_src = body.get('event_src')
             try:
-                data, sw = _send_event_download(scc, event_type, event_data)
+                data, sw = _send_event_download(scc, event_type, event_data, src=event_src)
                 try:
                     ev_type = int(event_type)
                 except (TypeError, ValueError):