feat: Add MainCommandMode.Hidden to completely hide NavigationBar MainCommand

[Copilot]

GitHub Issue (If applicable): closes #[issue_number]

PR Type

• Feature

What is the current behavior?

MainCommandMode has two values: Back (automatic back navigation) and Action (custom behavior with visible button). To completely hide the MainCommand, users must set MainCommandMode.Action and manually configure MainCommand.Visibility = Collapsed, which is non-obvious.

What is the new behavior?

Added MainCommandMode.Hidden that automatically collapses the MainCommand regardless of Frame backstack state.

Usage:

<utu:NavigationBar Content="Home" MainCommandMode="Hidden" />

Implementation:

• Enum: Added Hidden value to MainCommandMode enum
• Visibility Logic: UpdateMainCommandVisibility() now checks for Hidden mode first and sets Visibility.Collapsed
• Navigation Logic: TryPerformMainCommand() returns false for Hidden mode (no automatic navigation)
• Platform Support: Works across Windows/iOS/Android as native renderers already check Visibility.Visible

Tests:

• MainCommand_Hidden_Mode_Hides_Button(): Verifies button is collapsed
• MainCommand_Hidden_Mode_In_Frame_Stays_Hidden(): Verifies button stays hidden with backstack

PR Checklist

• Tested code with current supported SDKs
• Tested the changes where applicable:
  • UWP
  • WinUI
  • iOS
  • Android
  • WASM
  • MacOS
• Updated the documentation as needed:
  • General Doc Update
  • Controls Doc Update
  • Extensions Doc Update
  • controls-styles.md
  • lightweight-styling.md (LightWeight Styling Resource Keys)
• Runtime Tests and/or UI Tests for the changes have been added (for bug fixes / features) (if applicable)
• Contains NO breaking changes
• Associated with an issue (GitHub or internal)
• Commits must be following the Conventional Commits specification.

Other information

No platform-specific changes required. Native iOS/Android renderers respect Visibility property automatically.

Internal Issue (If applicable):

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[NavigationBar] Clarify how to completely hide the MainCommand</issue_title>
<issue_description>Currently, we document the usage of MainCommandMode being set to Action as a way to override the default behaviour of the MainCommand from the NavigationBar here: https://platform.uno/docs/articles/external/uno.toolkit.ui/doc/controls/[NavigationBar](https://platform.uno/docs/articles/external/uno.toolkit.ui/doc/controls/NavigationBar.html#maincommandmode).html#maincommandmode

We should document clearly that this will result in the MainCommand still being visible as it is assuming you still want it to display and customize the behavior when clicked.

There are scenarios where you may want to completely hide the MainCommand at all times. For that to work, we would need to document that you should be setting the MainCommandMode to Action as well as defining a MainCommand with the Visibility of the AppBarButton set to Collapsed. We should also perhaps add a new Hidden option for the MainCommandMode that would effectively do this for the user.</issue_description>

<agent_instructions>We should also implement the suggestion of the Hidden value for the MainCommandMode as detailed in the last sentence on the issue description</agent_instructions>

Comments on the Issue (you are @copilot in this section)

Custom agent used: toolkit-bug-fix-bot
Identifies critical bugs in your project and implements targeted fixes with working code

• Fixes [NavigationBar] Clarify how to completely hide the MainCommand #1503

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[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}