ci: trigger price-aware routing workflow

[mdheller]

Purpose

Trigger the newly added model-router-ci workflow on a pull request so GitHub Actions status can be confirmed for the price-aware routing tranche.

Change

Adds a documentation-only CI trigger note under docs/ci/.

Expected validation

python3 tools/validate_local_personal_route_bindings.py
python3 tools/validate_agent_execution_model_routing_policies.py
python3 tools/validate_agent_execution_budget_resource_optimizers.py
python3 tools/validate_model_price_catalogs.py
pytest -q tests/test_agent_execution_route_decision.py

Semantics

No runtime semantics changed. This is a CI trigger PR only.