feat: the Data Connection Status Change event gets its parameter form (0x1D)

EVENT_FORMS[0x1D] was missing, so its Send button posted event_data: null -
the ENVELOPE carried only the event list and device identities, none of the
event's data objects.  The form now builds the TS 31.111 7.5.25.2 object set
(tags per TS 101 220 / TS 31.111 9.3): data connection status (9D), connection
type (AA), optional (E/5G)SM cause (AE), transaction identifier (1C), optional
location information (13, CR flag 0 as the spec requires for this command),
optional access technology (BF), location status (9B), optional APN (C7) and
PDP/PDN/PDU type (0B).

Adjacent spec fixes found while verifying:
- the Access Technology Change options (0x0B) did not match the pinned
  TS 102 223 V18.3.0 8.61 coding (GSM Compact / GSM w-EGPRS / UTRAN w-HSDPA
  ...); they now use the shared ACCESSTECH list, whose two labels were also
  corrected (TIA/EIA-553-A, TIA/EIA-136-270);
- _send_event_download() wrote the D6 length as a single byte - a long APN
  would overflow it; 128..255 bytes now use the BER long form (81 <len>).

Tests: the 0x1D build (defaults, full form, fallbacks), the 8.61 option list,
the long-form D6.  Help EN/RU and both AGENTS files; sw cache simple-v342.

tests/test_ota_helpers.py

@@ -817,6 +817,17 @@ class TestEventDownload(unittest.TestCase):
         self.assertEqual(sw, '9000')
         self.assertEqual(apdu, '80c2000009d60799010582028281')
 
+    def test_event_with_long_data_uses_the_ber_long_form(self):
+        # 128+ bytes of event data: the D6 length becomes '81' <len> (the
+        # 7.5.x tables allow 1 or 2 length bytes; a raw byte above 0x7F would
+        # be read as a long-form indicator)
+        payload = bytes(range(200))
+        apdu, sw = self._send(0x1D, payload)
+        self.assertEqual(sw, '9000')
+        inner = bytes([0x99, 0x01, 0x1D, 0x82, 0x02, 0x82, 0x81]) + payload
+        d6 = bytes([0xD6, 0x81, len(inner)]) + inner
+        self.assertEqual(apdu, '80c20000%02x%s' % (len(d6), d6.hex()))
+
 
 class TestTimerManagement(unittest.TestCase):
     """Terminal side of TIMER MANAGEMENT (TS 102 223 6.6.21, 6.8.13/14, 7.4).