statusLine: expose update_available in JSON payload + setting to hide native update badge

Feature Request

Currently the native "update available" message in the status bar cannot be suppressed or restyled. Two related requests:

1. Expose update availability in the statusLine JSON payload

Add a field like update_available: true alongside version in the JSON piped to the custom statusLine.command script, so scripts can render their own update indicator.

2. Add a setting to hide the native update badge

E.g. "hideUpdateNotification": true in settings.json, for users who prefer a fully custom status line without the built-in text duplicating the information.

Use case

Users with a custom statusLine.command script want a cohesive, styled status bar (e.g. a single orange ↻ icon aligned to the right) without the native "update available" text badge appearing alongside it.

Current behavior

• The JSON payload sent to statusLine.command contains no update-related fields
• The native update badge cannot be hidden or restyled via any known setting

Expected behavior

• Custom status line scripts can detect and render update availability in their own style
• A setting allows hiding the native badge when a custom status line handles it instead