Add no cyclic routing mode

[toruseo]

With W = World(..., no_cyclic_routing=True), vehicles try to avoid traveling the same link or node twice to avoid unrealistic cyclic routes.

This addresses #272

[Copilot]

Pull request overview

Adds an opt-in “no cyclic routing” mode to UXsim’s route choice so vehicles preferentially avoid revisiting nodes/links, addressing cyclic-route frequency concerns raised in issue #272.

Changes:

• Introduces World(..., no_cyclic_routing=True) and applies node revisit-avoidance during next-link selection.
• Adds a verification test intended to detect repeated/symmetric link traversals under this mode.
• Updates README and bumps the “run examples” CI matrix Python version.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 7 comments.

File	Description
uxsim/uxsim.py	Adds no_cyclic_routing flag, applies avoidance logic in route_next_link_choice, and documents the new option.
tests/test_verification_route_choice.py	Adds a new verification test for the no-cyclic routing behavior on a generated grid network.
README.md	Adds documentation badge and updates feature bullets.
.github/workflows/run-examples.yml	Updates the Python version matrix used when running example-based tests.