A11y: Fix model picker Names, unique accelerator labels, and code sample Name length

[haoliuu]

Fixes for accessibility bugs reported against AI Dev Gallery. Each fix is in its own commit for independent review.

Fixes

• Model picker buttons: Panel-content buttons (Run sample, Add model, Open AI Toolkit, View documentation) now expose a UIA Name instead of null.
• Hardware accelerator badges: CPU/GPU/NPU "More info" buttons now have unique Names (e.g. "GPU more info") so focusable siblings aren't identical.
• Markdown lists: Decorative list-item wrappers and bullet glyphs are excluded from the accessibility tree to avoid whitespace-only Names.
• API code sample: The code RichTextBlock/ScrollViewer now exposes a concise Name instead of the full source (was exceeding 512 characters).

Validation

Verified manually with Accessibility Insights for Windows on the reported pages; project builds clean for x64.

[Copilot]

Pull request overview

This PR addresses several accessibility (UIA) issues in AI Dev Gallery by ensuring key interactive UI elements have meaningful, non-null, and non-duplicated accessible names, and by reducing excessively long accessible names for code samples.

Changes:

• Adds explicit AutomationProperties.Name values for model picker actions (e.g., Run sample / Add model / View documentation / Open AI Toolkit tool) and the API code sample surface.
• Makes hardware-accelerator “More info” buttons uniquely named per accelerator (CPU/GPU/NPU/…).
• Adjusts Markdown list rendering to suppress decorative bullet UI from the accessibility tree (but see comment on list-item content visibility).

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
AIDevGallery/Utils/AppUtils.cs	Adds helper to generate unique accelerator “more info” UIA Names.
AIDevGallery/Pages/APIs/APIPage.xaml	Sets a concise UIA Name for the code sample ScrollViewer.
AIDevGallery/Controls/ModelSelectionControl.xaml	Uses the new accelerator “more info” UIA Name helper in templates.
AIDevGallery/Controls/ModelPicker/ModelPickerViews/OnnxPickerView.xaml	Adds UIA Names for action buttons and unique accelerator “more info” Names.
AIDevGallery/Controls/ModelPicker/ModelOrApiPicker.xaml	Adds unique accelerator “more info” Names and a UIA Name for “Run sample”.
AIDevGallery/Controls/ModelPicker/AddHFModelView.xaml	Uses the new accelerator “more info” UIA Name helper in templates.
AIDevGallery/Controls/Markdown/TextElements/MyList.cs	Excludes bullet glyphs from the accessibility tree (but currently also excludes list item content).

[haoliuu]

fixed