fix(wecom): accept aibot hex keys and strip group mentions

[sgaofen]

Summary

• accept 64-character hex aeskey values from the WeCom aibot websocket while preserving the existing base64 callback flow
• strip a configured plain-text @BotName prefix from group messages before slash-command detection
• expose bot_display_name via config/env wiring and document it in the CLI config example

Root Cause

WeCom aibot image payloads can deliver aeskey as a 64-character hex string, but _decrypt_file_bytes() only tried base64 decoding. Group chat messages also arrive with a literal @DisplayName prefix and no structured mention metadata, so commands like @Hermes /reset never reached the existing slash-command path.

Testing

• python3 -m py_compile /Users/stephenyu/Documents/hermes-agent-wt-11447/gateway/platforms/wecom.py /Users/stephenyu/Documents/hermes-agent-wt-11447/gateway/config.py /Users/stephenyu/Documents/hermes-agent-wt-11447/tests/gateway/test_wecom.py
• uv run --directory /Users/stephenyu/Documents/hermes-agent-wt-11447 --extra dev pytest -o addopts='' /Users/stephenyu/Documents/hermes-agent-wt-11447/tests/gateway/test_wecom.py -q

Platform Tested

• macOS

Contribution Guide Notes

• updates cli-config.yaml.example for the new platforms.wecom.extra.bot_display_name knob
• resolves fix(wecom): aibot image decryption fails + group @mention not stripped #11447

[sgaofen]

CI note: the failing test check appears to be an unrelated upstream failure, not a regression in this WeCom patch. Both this PR and #11752 are red on the same test: tests/hermes_cli/test_opencode_go_in_model_list.py::test_opencode_go_appears_when_api_key_set, with the opencode-go model order coming back as ['kimi-k2.5', 'glm-5.1', 'glm-5', ...] instead of the asserted order. The WeCom-specific targeted regression suite still passes locally (34 passed).

[teknium1]

Thanks for isolating the WeCom AES-key issue. The remaining hex-key defect is real on current main: plugins/platforms/wecom/adapter.py:1069-1073 only pads and base64-decodes aeskey values.

Problems

• The group-command half is already implemented by 8b1ff55f5382052a5d98246659136e632af13697; current main strips the leading group @mention at plugins/platforms/wecom/adapter.py:526-532.
• The adapter moved from gateway/platforms/wecom.py to plugins/platforms/wecom/adapter.py in 46f2cc2844c1448f9bc35166c46b97c30af53dd0. Porting the old fallback directly would also lose the unpadded-base64 handling added in 8f4c0bf0882c3c7258a65e3adade12d5b08068ea.

Suggested changes

• Port the exact 64-hex-character branch before the existing base64-padding path in plugins/platforms/wecom/adapter.py.
• Keep main's existing mention handling; the new display-name config is no longer needed for the reported @BotName /command case.
• Preserve the hex regression test in tests/gateway/test_wecom.py and update website/docs/user-guide/messaging/wecom.md:208-210, which currently documents base64 only.

This is an automated hermes-sweeper review.