Polish defaults and updater feedback

[adibhanna]

What changed

• switched first-run defaults to use the built-in font defaults instead of forcing SF Mono
• changed the default shipped theme to Gruvbox Dark Hard and enabled tabs by default
• fixed packaged app metadata so the About panel and bundle metadata use Adib Hanna
• made manual update checks show an explicit result instead of looking like a no-op
• normalized GitHub release notes from the updater feed so HTML tags are not shown verbatim in Settings

Why

The first public build exposed a few rough edges on first launch and in the About/Updates screen. The app was opening with the wrong default look, the About metadata had the wrong name, and the updater feedback path was too subtle when the user was already on the latest version.

User impact

• new installs open with the intended default theme and tabs visible
• fonts stay on the app's Default path unless the user chooses a specific family
• About metadata is correct in packaged builds
• update checks now give immediate feedback and display cleaner release notes

Validation

• npm run typecheck