feat(gateway): add WeCom (Enterprise WeChat) platform support (#3847)

Adds WeCom as a gateway platform adapter using the AI Bot WebSocket
gateway for real-time bidirectional communication. No public endpoint
or new pip dependencies needed (uses existing aiohttp + httpx).

Features:
- WebSocket persistent connection with auto-reconnect (exponential backoff)
- DM and group messaging with configurable access policies
- Media upload/download with AES decryption for encrypted attachments
- Markdown rendering, quote context preservation
- Proactive + passive reply message modes
- Chunked media upload pipeline (512KB chunks)

Cherry-picked from PR #1898 by EvilRan with:
- Moved to current main (PR was 300 commits behind)
- Skipped base.py regressions (reply_to additions are good but belong
  in a separate PR since they affect all platforms)
- Fixed test assertions to match current base class send() signature
  (reply_to=None kwarg now explicit)
- All 16 integration points added surgically to current main
- No new pip dependencies (aiohttp + httpx already installed)

Fixes #1898

Co-authored-by: EvilRan <EvilRan@users.noreply.github.com>

toolsets.py

@@ -357,6 +357,12 @@ TOOLSETS = {
         "includes": []
     },
 
+    "hermes-wecom": {
+        "description": "WeCom bot toolset - enterprise WeChat messaging (full access)",
+        "tools": _HERMES_CORE_TOOLS,
+        "includes": []
+    },
+
     "hermes-sms": {
         "description": "SMS bot toolset - interact with Hermes via SMS (Twilio)",
         "tools": _HERMES_CORE_TOOLS,
@@ -366,7 +372,7 @@ TOOLSETS = {
     "hermes-gateway": {
         "description": "Gateway toolset - union of all messaging platform tools",
         "tools": [],
-        "includes": ["hermes-telegram", "hermes-discord", "hermes-whatsapp", "hermes-slack", "hermes-signal", "hermes-homeassistant", "hermes-email", "hermes-sms", "hermes-mattermost", "hermes-matrix", "hermes-dingtalk", "hermes-feishu"]
+        "includes": ["hermes-telegram", "hermes-discord", "hermes-whatsapp", "hermes-slack", "hermes-signal", "hermes-homeassistant", "hermes-email", "hermes-sms", "hermes-mattermost", "hermes-matrix", "hermes-dingtalk", "hermes-feishu", "hermes-wecom"]
     }
 }