fix: root pytest failures

[namabeeru]

What

• Limit default root pytest discovery to the maintained tests/ suite.
• Update the router test fake LLM to accept the current generate_response_async(..., prompt_name=...) call shape.
• Assert the session router passes ROUTE_TO_SESSION into the LLM call.

Why

Root pytest was collecting generated/template Living UI tests under app/data, which are not part of CraftBot's maintained root suite and can fail collection from the repository root. The router tests also had a stale fake LLM signature after router calls started passing prompt_name for prompt capture.

This replaces #360 with a clean branch based directly on dev; the old PR had the right file diff but included unrelated main merge commits in its PR commit list after retargeting.

How to test

• /usr/local/bin/python3.10 -m pytest tests/test_trigger_router_and_parking.py -q -> 9 passed
• /usr/local/bin/python3.10 -m pytest --collect-only -q -> 99/115 tests collected (16 deselected)
• /usr/local/bin/python3.10 -m pytest -q -> 99 passed, 16 deselected
• Root pytest loop: 20/20 successful runs, each 99 passed, 16 deselected
• /usr/local/bin/python3.10 -m pytest app/data/living_ui_template/backend/tests -q -> 4 passed when invoked explicitly
• /usr/local/bin/python3.10 -m ruff format --check . -> 588 files already formatted
• /usr/local/bin/python3.10 -m ruff check . -> All checks passed!
• /usr/local/bin/python3.10 -m compileall -q app agent_core agents decorators skills -> passed
• /usr/local/bin/python3.10 -m py_compile tests/test_trigger_router_and_parking.py -> passed
• git diff --check HEAD^..HEAD -> passed