docs: Improve Getting Started

[DevTKSS]

GitHub Issue (If applicable): closes #

PR Type

What kind of change does this PR introduce?

• Documentation content changes

What is the current behavior?

• Note about "Uno Check found problems" missing
• MainWindow and Host Property ordering of advises to change them is a bit confusing in this order, as the whole app is building on top of them.
• As the extension docs are expandable in volume, there has been missing a proper overview of the App.xaml.cs contents
• Only Frame Navigation Set-Up was mentioned in the code. As these Getting Started belongs to the uno.extensions, there should at least be that start point from the App.xaml.cs to frame AND Navigation Extension.

What is the new behavior?

• Added Information about Uno Check found problems Banner
• Improved the ordering for Window and Hostbuilder, to build the app step by step and not from end to beginning -> makes it easier to follow the guide
• Added Diff including comments to difference between, what belongs to which feature and at which level in which order we need to put them, when we do not want to create a app to just see where to do this, when we might be migrating or adding from a blank preset app.
• Added short information, how in exchange the Navigation Extension would be used with Builder.

PR Checklist

Please check if your PR fulfills the following requirements:

• Docs have been added/updated which fit documentation template. (for bug fixes / features)
• Contains NO breaking changes
• Associated with an issue (GitHub or internal)

Other information

Internal Issue (If applicable):

[unodevops]

⚠️⚠️ The build 168775 has failed on uno.extensions.

[DevTKSS]

@dr1rrb I think to remember you wanted to look at this for e.g. the banner, at the time I send the temp HD licensing PR 🙃 could you or somebody else of the team check on this?
@jeromelaban or do you know of somebody that could throw an eye (no amputees please ;) ) on this for review? maybe nobody noticed this PR so far as it gots no comments of a team member so far

[DevTKSS]

@kazo0 for the rest of the hostbuilder updates here in the upgrading file here you mentioned, if you would delete that, I think we would then need the steps in the hostbuilder somewhere else🤔 I had initially the problems starting with those, that the seperate ones in the extensions how to were not showing me in which order I need to add them🤔 of course something like putting that initializing Configure infront but Maybe putting options before configure services and the others also. I would not remember that any of them are mentioning any relationship or order to the options they are all importing or and using.

Maybe we could also indeed add even secondary for each a sentence that is introducing us to the expected appsettings nested name?
As example: I was attempting to use appsetting.oidc.json not knowing that it has a default search name and the build verbose output hinted me, that it did not found any appsettings.oidcsettings.json.
Same for the other extensions of course like storage etc.🤔
We are told about the section default name, which would be in this case Oidc then, but nothing about oidcsettings there.

[Copilot]

Pull Request Overview

This PR improves the Getting Started documentation for Uno.Extensions by clarifying setup steps and providing more comprehensive guidance. The changes focus on making the installation and configuration process more user-friendly and complete.

• Enhanced clarity around prerequisites and setup requirements
• Improved step-by-step guidance for configuring Uno.Extensions with better ordering
• Added comprehensive code examples showing both Frame Navigation and Uno.Extensions Navigation approaches

Reviewed Changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 2 comments.

File	Description
doc/Learn/includes/single-project.md	Added clarification text about completing migration before proceeding
doc/Learn/includes/existing-app.md	Improved wording for clarity about existing application setup
doc/GettingStarted.md	Major restructuring with enhanced code examples, better step ordering, and comprehensive configuration details

[kazo0]

whitespace not correct