Implement shared splash-screen and application-service capabilities

## Objective

Implement approved splash-screen lifecycle/minimum-display behavior and shared application information/network-availability services. Keep the APIs testable and language-neutral, marshal events correctly, avoid startup blocking, and account for existing behavior such as #4279 and #9807.

## Completion guidance

- Keep the implementation focused on the objective while allowing the assignee to improve the approach based on research.
- Document important decisions, rejected alternatives, dependencies, and follow-up work.
- Add or update tests and documentation appropriate to the work.
- Verify locally and in CI where the task changes code or generated artifacts.

Start by researching the approved splash-screen lifecycle and minimum-display behavior, along with the shared application information and network-availability services. Review existing behavior referenced by issues #4279 and #9807, then identify appropriate tests and documentation. Done means the APIs are testable and language-neutral, events marshal correctly, startup does not block, and local and CI verification is recorded.

Written by the indexing model from the issue text.