fix(gateway/weixin): split poll/send sessions, reuse live adapter for cron & send_message

- gateway/platforms/weixin.py:
  - Split aiohttp.ClientSession into _poll_session and _send_session
  - Add _LIVE_ADAPTERS registry so send_weixin_direct() reuses the connected gateway adapter instead of creating a competing session
  - Fixes silent message loss when gateway is running (iLink token contention)

- cron/scheduler.py:
  - Support comma-separated deliver values (e.g. 'feishu,weixin') for multi-target delivery
  - Delay pconfig/enabled check until standalone fallback so live adapters work even when platform is not in gateway config

- tools/send_message_tool.py:
  - Synthesize PlatformConfig from WEIXIN_* env vars when gateway config lacks a weixin entry
  - Fall back to WEIXIN_HOME_CHANNEL env var for home channel resolution

- tests/gateway/test_weixin.py:
  - Update mocks to include _send_session

tools/send_message_tool.py

@@ -215,7 +215,27 @@ def _handle_send(args):
 
     pconfig = config.platforms.get(platform)
     if not pconfig or not pconfig.enabled:
-        return tool_error(f"Platform '{platform_name}' is not configured. Set up credentials in ~/.hermes/config.yaml or environment variables.")
+        # Weixin can be configured purely via .env; synthesize a pconfig so
+        # send_message and cron delivery work without a gateway.yaml entry.
+        if platform_name == "weixin":
+            import os
+            wx_token = os.getenv("WEIXIN_TOKEN", "").strip()
+            wx_account = os.getenv("WEIXIN_ACCOUNT_ID", "").strip()
+            if wx_token and wx_account:
+                from gateway.config import PlatformConfig
+                pconfig = PlatformConfig(
+                    enabled=True,
+                    token=wx_token,
+                    extra={
+                        "account_id": wx_account,
+                        "base_url": os.getenv("WEIXIN_BASE_URL", "").strip(),
+                        "cdn_base_url": os.getenv("WEIXIN_CDN_BASE_URL", "").strip(),
+                    },
+                )
+            else:
+                return tool_error(f"Platform '{platform_name}' is not configured. Set up credentials in ~/.hermes/config.yaml or environment variables.")
+        else:
+            return tool_error(f"Platform '{platform_name}' is not configured. Set up credentials in ~/.hermes/config.yaml or environment variables.")
 
     from gateway.platforms.base import BasePlatformAdapter
 
@@ -225,6 +245,12 @@ def _handle_send(args):
     used_home_channel = False
     if not chat_id:
         home = config.get_home_channel(platform)
+        if not home and platform_name == "weixin":
+            import os
+            wx_home = os.getenv("WEIXIN_HOME_CHANNEL", "").strip()
+            if wx_home:
+                from gateway.config import HomeChannel
+                home = HomeChannel(platform=platform, chat_id=wx_home, name="Weixin Home")
         if home:
             chat_id = home.chat_id
             used_home_channel = True