Run commands: open a URL in the default browser after command completes

[AThraen]

This was generated by AI during triage.

Summary

Add an optional post-run URL field to RunCommandItem. When set and the command exits with code 0, CodeShellManager opens the URL in the user's default browser automatically.

Motivation

A very common dev workflow is: run a build/dev-server command → wait for it to be ready → open http://localhost:5173 (or similar). Today the user has to manually switch to a browser after the run completes. Automating this mirrors what IDEs like Rider and VS Code do with "open browser on start".

Useful examples:

• dotnet run → open http://localhost:5000
• npm run dev → open http://localhost:5173
• mkdocs serve → open http://localhost:8000
• A deploy script → open a staging URL

Proposed behaviour

Data model

Add PostRunUrl: string? to RunCommandItem. null / empty = no browser launch (default, backwards-compatible).

Runtime

After a run completes (exit code 0 only, unless a future option adds "open even on failure"):

1. If PostRunUrl is set and non-empty, call Process.Start(new ProcessStartInfo(url) { UseShellExecute = true }) to hand it to the OS default browser.
2. Show a brief toast: "Opened [url] in browser".
3. If the process fails to launch, show a warning toast instead of silently failing.

Editor UI (SessionRunCommandsDialog)

• Add an optional "Open URL" text field below (or beside) the command-line field for each row.
• Placeholder text: https://localhost:5000 or similar.
• No URL validation beyond "non-empty string" — the OS will handle invalid URLs.

Persistence

PostRunUrl serialises to state.json alongside other RunCommandItem fields.

Out of scope

• Waiting for the server to be ready before opening (health-check polling). That is a separate, more complex feature.
• Opening a URL on non-zero exit.