feat(langfuse): tag traces with active profile

[aqilaziz]

Summary

• thread the active Hermes profile into LLM and tool plugin hooks
• set Langfuse trace user_id from the active profile and keep metadata.profile for redundancy
• document per-profile Langfuse filtering in the bundled plugin README
• add regression coverage for profile userId, run_agent hook payloads, and model_tools hook payloads
• include CI stabilizers for Discord mock imports and Nous provider model defaults

Fixes #26455.

Tests

• python -m pytest -o addopts= tests\plugins\test_langfuse_plugin.py::TestProfileUserId tests\run_agent\test_run_agent.py::TestRunConversation::test_request_scoped_api_hooks_fire_for_each_api_call tests\test_model_tools.py::TestHandleFunctionCall::test_tool_hooks_receive_session_and_tool_call_ids -q --tb=short
• python -m pytest -o addopts= tests\plugins\test_langfuse_plugin.py -q --tb=short
• python -m pytest -o addopts= tests\test_model_tools.py -q --tb=short
• python -m pytest -o addopts= tests\run_agent\test_run_agent.py::TestRunConversation::test_request_scoped_api_hooks_fire_for_each_api_call -q --tb=short
• python -m pytest -o addopts= tests\e2e\test_discord_adapter.py -q --tb=short
• python -m pytest -o addopts= tests\run_agent\test_provider_parity.py::TestDeveloperRoleSwap::test_developer_role_via_nous_portal tests\run_agent\test_provider_parity.py::TestBuildApiKwargsNousPortal::test_includes_nous_product_tags tests\run_agent\test_provider_parity.py::TestBuildApiKwargsNousPortal::test_uses_chat_completions_format -q --tb=short
• python -m ruff check plugins\observability\langfuse\__init__.py tests\plugins\test_langfuse_plugin.py run_agent.py model_tools.py hermes_cli\plugins.py tests\run_agent\test_run_agent.py tests\test_model_tools.py tests\e2e\conftest.py tests\run_agent\test_provider_parity.py
• python -m py_compile plugins\observability\langfuse\__init__.py run_agent.py model_tools.py hermes_cli\plugins.py
• git diff --check

[adoreparler]

Any luck with this PR?