fix(discord): add initiator to handoff threads

[whirmill]

Summary

• Adds an optional user_ids argument to handoff-thread creation so platforms with explicit thread membership APIs can include the initiating operator.
• Implements best-effort Discord thread.add_user(...) for explicit handoff initiators.
• Avoids falling back to all allowed Discord users, so automated handoff threads do not become noisy in multi-operator servers.

Testing

• python -m pytest tests/gateway/test_discord_send.py -o 'addopts=' -q
• Included in combined local convergence run: 272 passed

[teknium1]

Thanks for addressing Discord handoff discoverability. The underlying gap remains on current main: gateway/run.py:7501-7503 creates handoff threads without a member identity, and plugins/platforms/discord/adapter.py:5455-5531 has no membership step.

Problems

• The proposed row.get("user_id") source cannot identify the normal CLI handoff initiator. Current agent-created rows explicitly use user_id=None in run_agent.py:600-608, and direct CLI row creation likewise omits it in cli.py:7091-7099; the new kwargs would therefore be empty in the primary /handoff flow.
• The added unit tests exercise only the adapter API. Add an end-to-end _process_handoff test with a CLI-shaped row so the identity propagation is verified.
• The Discord adapter moved from gateway/platforms/discord.py to plugins/platforms/discord/adapter.py in cc8e5ec2afbfd10a3cff4e710210dd9ecae64a33, so this needs a deliberate port.

Suggested changes

• Establish a reliable destination Discord user identity when the handoff is requested, persist it with the handoff request, then pass that explicit identity to the plugin adapter.

Automated hermes-sweeper review.

[teknium1]

row["user_id"] is not populated for the normal CLI handoff flow: current agent-created rows pass user_id=None (run_agent.py:600-608) and CLI row creation omits it (cli.py:7091-7099). Persist a trustworthy destination Discord operator ID at request time, then test _process_handoff with that CLI-shaped row.

[whirmill]

Superseded by the current-main replacement PR #65505: #65505

[whirmill]

Superseded by current-main replacement PR #65505: #65505