fix(windows): offer WebView2 runtime download when it is missing

[Firnschnee]

The third item from my real-hardware testing notes on #8: the WebView2-runtime-missing error message.

The problem

On a machine without the WebView2 Evergreen runtime (Windows LTSC/Server and some clean installs ship without it -- my test box was exactly this), OnLoaded hit the generic catch (Exception) and showed a developer-facing message pointing at docs/WINDOWS.md. Useless to an end user who just double-clicked a Start Menu shortcut and has no idea what a "maintainer checklist" is.

The fix

Catch WebView2RuntimeNotFoundException specifically and offer to open Microsoft's download page (Yes/No -> default browser via the existing OpenInDefaultBrowser helper). Kept separate from the generic handler on purpose: the installer is only suggested when the runtime is genuinely the problem, not for an arbitrary crash. The catch-all handler now also names the download URL as a hint.

Verification (Windows 11)

Couldn't uninstall my runtime, so I forced the failure by pointing WEBVIEW2_BROWSER_EXECUTABLE_FOLDER at a non-existent folder:

• The not-found path triggers and shows the Yes/No dialog (<App> needs the Microsoft Edge WebView2 runtime...).
• Clicking Yes opens the WebView2 download page in the default browser.
• Compiles clean against the pinned WebView2 package (WebView2RuntimeNotFoundException is in Microsoft.Web.WebView2.Core, already imported); only the pre-existing DPI manifest warning remains.

Notes

• Independent of fix(windows): bake app name into assembly so taskbar right-click shows it (#9) #17 -- touches only MainWindow.xaml.cs (+ changelog). Both edit the changelog near the same line, so whichever merges second will want a trivial conflict resolution.
• The runtime-missing dialog itself can't be exercised by the windows-latest CI (the runner has the runtime), same as it can't be from macOS -- hence the manual hardware check above.

Summary by Sourcery

Improve Windows WebView2 runtime error handling to guide end users when the runtime is missing.

Bug Fixes:

• Handle missing WebView2 runtime on Windows by detecting the specific runtime-not-found exception and offering to open Microsoft's download page so users can install it themselves.

Documentation:

• Update the changelog to document the improved WebView2 runtime-missing behavior in the Windows beta scaffold.

[sourcery-ai]

Reviewer's Guide

Adds explicit handling for missing WebView2 runtime on Windows by prompting end users to install it from Microsoft’s download page, and updates the changelog to document the behavior change.

Sequence diagram for handling missing WebView2 runtime on window load

sequenceDiagram
    actor User
    participant MainWindow
    participant Web
    participant MessageBox
    participant DefaultBrowser

    User->>MainWindow: OnLoaded
    MainWindow->>Web: EnsureCoreWebView2Async
    alt WebView2 runtime missing
        Web-->>MainWindow: WebView2RuntimeNotFoundException
        MainWindow->>MessageBox: MessageBox.Show(YesNo Warning)
        MessageBox-->>MainWindow: MessageBoxResult.Yes
        opt User clicks Yes
            MainWindow->>DefaultBrowser: OpenInDefaultBrowser(WebView2DownloadUrl)
        end
    else Other WebView2 failure
        Web-->>MainWindow: Exception
        MainWindow->>MessageBox: MessageBox.Show(OK Error with WebView2DownloadUrl)
    end

Loading

File-Level Changes

Change	Details	Files
Handle missing WebView2 runtime explicitly and guide end users to install it.	Introduce a constant holding Microsoft’s canonical WebView2 Evergreen runtime download URL. Add a dedicated catch block for WebView2RuntimeNotFoundException that shows a Yes/No dialog explaining the missing runtime and offering to open the download page in the default browser. Adjust the generic exception handler message to reference the WebView2 download URL as a hint in addition to pointing maintainers at docs/WINDOWS.md.	plugins/app-it-windows/skills/app-it-windows/templates/wrapper-windows/MainWindow.xaml.cs
Document the Windows WebView2 runtime-missing behavior change.	Add a changelog entry describing the new behavior when the WebView2 runtime is missing, including the specific exception handled and the end-user flow.	CHANGELOG.md

Possibly linked issues

• fix(windows): embed correct AssemblyName / FileDescription so taskbar right-click shows the app name #9: PR implements the issue by catching WebView2RuntimeNotFoundException and surfacing Microsoft’s WebView2 runtime download URL to users.

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[sourcery-ai]

Hey - I've left some high level feedback:

• The WebView2 download URL is now hard-coded in MainWindow; consider centralizing it in a shared config or constants module so it can be reused or updated without touching UI code.
• The new user-facing message strings are embedded directly in code and use explicit "\n" separators; consider using Environment.NewLine and a localization-friendly pattern (e.g., resource files) to make future translation or wording changes easier.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- The WebView2 download URL is now hard-coded in MainWindow; consider centralizing it in a shared config or constants module so it can be reused or updated without touching UI code.
- The new user-facing message strings are embedded directly in code and use explicit "\n" separators; consider using `Environment.NewLine` and a localization-friendly pattern (e.g., resource files) to make future translation or wording changes easier.

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[Christian-Katzmann]

Merged — thank you, @Firnschnee. Catching WebView2RuntimeNotFoundException specifically, so the installer is only offered when the runtime is genuinely the problem (and not for an arbitrary crash), is the right call — and forcing the failure via WEBVIEW2_BROWSER_EXECUTABLE_FOLDER to test it without uninstalling your own runtime was resourceful.

Credited in the README's Community nudge alongside your other Windows fixes. Thanks again.