Enable ament_mypy (--ament-strict) on remaining Python demos

[trippyogi]

Summary

• Add ament_mypy + test/test_mypy.py with --ament-strict for demo_nodes_py and quality_of_service_demo_py (remaining packages under Make demo python packages pass with ament_mypy #765 / Add ament_mypy to demo_nodes_py #767 / Add ament_mypy to rclpy in quality_of_service_demo #769).
• Add type annotations across those packages so they can pass strict mypy (callbacks, Parameter generics, QoS event info types, main/__init__ return types).
• In liveliness.py, align the publisher liveliness callback with QoSLivelinessLostInfo fields (total_count / total_count_change) instead of subscription liveliness-changed fields.

Related open PRs that this overlaps (can close if this lands): #780 (demo_nodes_py), #793 (quality_of_service_demo_py).

Fixes #765
Fixes #767
Fixes #769

Test plan

• colcon build --packages-select demo_nodes_py quality_of_service_demo_py
• colcon test --packages-select demo_nodes_py quality_of_service_demo_py --event-handlers console_cohesion+
• Confirm test_mypy.py passes with --ament-strict on both packages
• Confirm flake8/pep257/copyright/xmllint still pass
• CI (Linux / aarch64 / RHEL / Windows) for rolling

Note: local validation was not run here (Windows host without a ROS 2 workspace); CI should validate ament_mypy.

[trippyogi]

Overlap note

This draft overlaps existing open work:

• Added test_mypy.py and resolved all regressions in demo_nodes_py (#767) #780 — demo_nodes_py mypy (non-draft, in progress since Apr)
• Add ament_mypy to quality_of_service_demo_py #793 — quality_of_service_demo_py ament_mypy wiring (non-draft)

Happy to close this in favor of those PRs, or slim this branch to only the QoS typing fixes if #793 lands the test hook first. Maintainer preference welcome.

[trippyogi]

Still holding for maintainer scope decision

No intent to advance this draft over the assigned GFI PRs:

• Keep Added test_mypy.py and resolved all regressions in demo_nodes_py (#767) #780 / Add ament_mypy to quality_of_service_demo_py #793 as the primary paths unless a maintainer asks this PR to supersede or to shrink to only the QoS typing leftover from Add ament_mypy to quality_of_service_demo_py #793.
• Happy to close, rebase-to-supersede, or reduce scope on request.

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[fujitatomoya]

i think this conflicts against #780 and #793, this conflicts need to be resolved.

and before review, please make sure that all the tests are pass with your code change in local environment.

@InvincibleRMC can you also take a look at this?

[trippyogi]

Thanks @fujitatomoya, agreed. #801 was an exploratory combined draft; happy to close it so #780 (#767) and #793 (#769) stay the primary paths. If useful after those land, I can open a follow-up for any remaining QoS typing under --ament-strict. Open to take whichever direction you and @InvincibleRMC prefer.

[InvincibleRMC]

I would close the other ones. And proceed with this one. Let me know once that is done and I can review it.

[fujitatomoya]

@InvincibleRMC i will leave this up to you, but #780 and #793 original authors are responsive reliably, so i would not want to just go ahead to close their effort on those PRs. i would take part of those PRs, and then come back on this PR what is left to address.

[InvincibleRMC]

Sorry @fujitatomoya I agree with what you said. I mistakenly thought it was the same developer wanting to close their small PRS and join them into one larger one for less review churn.