Improve TraCI traffic light tutorial

[Corvus-226]

Summary

This PR improves the TraCI traffic-light tutorial by separating route
generation from the online controller and replacing ambiguous numeric IDs
with descriptive element names.

Changes

• move deterministic route generation from runner.py to generateRoutes.py;
• keep runner.py as the one-command tutorial entry point;
• rename the traffic-light ID to junction;
• rename the northbound induction-loop ID to north_detector;
• update cross.net.xml consistently with the source files while preserving the legacy network structure and simulation behavior;
• include generateRoutes.py in the complex-test tutorial extraction;
• update the tutorial documentation to describe the new file roles and IDs.

Validation

• python -m py_compile runner.py generateRoutes.py
• python generateRoutes.py
• python runner.py --nogui
• deterministic route output remains unchanged: 768 vehicles
• simulation output remains unchanged: end time 3728.00 and all 768 trip records match the baseline
• targeted TextTest tutorial/traci_tls/plain passes
• extracted tutorial example runs successfully
• mkdocs build
• git diff --check

Note

The committed cross.net.xml changes are intentionally limited to the renamed
ID references. Regenerating this legacy tutorial network with current
netconvert introduces unrelated format and behavioral changes.

Closes #8741

[namdre]

Thanks! Please ensure the legal niceties (ECA) are covered: https://sumo.dlr.de/docs/FAQ.html#how_do_i_contribute_to_the_documentation / https://sumo.dlr.de/docs/FAQ.html#how_do_code_contributions_work