fix(gateway): deduplicate Weixin messages by content fingerprint

[PratikRai0101]

What does this PR do?

This PR resolves an issue where the Weixin (ilinkai) adapter would occasionally deliver the same logical message twice within a short window (~3 seconds). Because the upstream API assigns unique message_id values to these duplicate deliveries, they bypassed the existing ID-based deduplicator, causing the agent to respond twice to the same user query.

The fix implements a secondary deduplication layer in the Weixin adapter that fingerprints messages based on a hash of the sender_id and the text content. This ensures that identical text from the same sender within the deduplicator's 5-minute TTL window is only processed once.

Related Issue

Fixes #16182

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 🔒 Security fix
• 📝 Documentation update
• ✅ Tests (adding or improving test coverage)
• ♻️ Refactor (no behavior change)
• 🎯 New skill (bundled or hub)

Changes Made

• gateway/platforms/weixin.py: Updated _process_message to calculate an MD5 content fingerprint (content:{sender_id}:{text_hash}) for messages containing text. If this fingerprint is already present in the deduplicator, the message is dropped early.
• tests/gateway/test_weixin.py: Added a new TestWeixinContentDedup class with regression tests to verify:
  1. Duplicate content with different message IDs is correctly caught and dropped.
  2. Messages without text (media-only) bypass the content-based logic to prevent false positives on consecutive media uploads.

How to Test

1. Automated Tests: Run the targeted test suite using:

   pytest tests/gateway/test_weixin.py -v
   

2. Manual Verification: Monitor gateway logs during a Weixin session. Verify that the debug log [Weixin] Content-dedup: skipping duplicate message from ... appears if the upstream API sends a redundant poll response.

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix
• I've run pytest tests/ -q and all relevant tests pass
• I've added tests for my changes
• I've tested on my platform: Arch Linux

Documentation & Housekeeping

• I've updated relevant documentation — N/A
• I've updated cli-config.yaml.example — N/A
• I've updated CONTRIBUTING.md or AGENTS.md — N/A
• I've considered cross-platform impact (Windows, macOS)
• I've updated tool descriptions/schemas — N/A

Screenshots / Logs

Test Execution Output:

tests/gateway/test_weixin.py::TestWeixinContentDedup::test_duplicate_content_with_different_message_ids_is_dropped PASSED
tests/gateway/test_weixin.py::TestWeixinContentDedup::test_content_dedup_not_called_for_messages_without_text PASSED

======================== 44 passed, 2 warnings in 4.68s =======================

[teknium1]

Salvaged via #19742 onto current main. Test-file conflict resolved by preserving both the TestIsStaleSessionRet class (from a separate landed fix) and your new TestWeixinContentDedup class. Thanks @PratikRai0101!