fix: add missing platforms to cron/send_message delivery maps and tool schema

Matrix, Mattermost, Home Assistant, and DingTalk were missing from the
platform_map in both cron/scheduler.py and tools/send_message_tool.py,
causing delivery to those platforms to silently fail.

Also updates the cronjob tool schema description to list all available
delivery targets so the model knows its options.

cron/scheduler.py

@@ -137,6 +137,9 @@ def _deliver_result(job: dict, content: str) -> None:
         "whatsapp": Platform.WHATSAPP,
         "signal": Platform.SIGNAL,
         "matrix": Platform.MATRIX,
+        "mattermost": Platform.MATTERMOST,
+        "homeassistant": Platform.HOMEASSISTANT,
+        "dingtalk": Platform.DINGTALK,
         "email": Platform.EMAIL,
         "sms": Platform.SMS,
     }

tools/cronjob_tools.py

@@ -370,7 +370,7 @@ Important safety rule: cron-run sessions should not recursively schedule more cr
             },
             "deliver": {
                 "type": "string",
-                "description": "Delivery target: origin, local, telegram, discord, signal, sms, or platform:chat_id"
+                "description": "Delivery target: origin, local, telegram, discord, slack, whatsapp, signal, matrix, mattermost, homeassistant, dingtalk, email, sms, or platform:chat_id"
             },
             "model": {
                 "type": "string",

tools/send_message_tool.py

@@ -124,6 +124,10 @@ def _handle_send(args):
         "slack": Platform.SLACK,
         "whatsapp": Platform.WHATSAPP,
         "signal": Platform.SIGNAL,
+        "matrix": Platform.MATRIX,
+        "mattermost": Platform.MATTERMOST,
+        "homeassistant": Platform.HOMEASSISTANT,
+        "dingtalk": Platform.DINGTALK,
         "email": Platform.EMAIL,
         "sms": Platform.SMS,
     }