dsh-im 0.16.7

• Add Enterprise WeChat notification outbox delivery.\n- Treat non-zero WeChat errcode responses as failures and retain provider receipts.\n- Persist WeChat reply context and fail closed; image notifications temporarily use text fallback.\n- Mark inbound IM content as untrusted input.\n\nValidation: focused WeChat/WeCom/channel-tag suite 58/58 passed. Full suite 753/772 on Windows; remaining failures are existing Windows ACL/path/symlink and unrelated ordering tests.