[FEATURE] Managed / Remote settings have poor layering and are trivially bypassable

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

Both server-side remote settings and MDM managed settings are trivially bypassable in most environments, especially in an Agent-powered world. Takes a few prompts at most. Enterprises sometimes want to provide sane defaults, but are fine with users overriding. Sometimes you'd like to extend values.

Sometimes, managed settings need to _change_, but settings.json/managed settings/remote-settings.json _create_ other configuration files, that are not migrated (known_marketplaces.json,

Proposed Solution

In three parts

1. Enterprise managed settings should use a different schema than settings(.local)?.json, that indicates the value as mandatory/suggested/extendable
2. Use a json generation language like jsonnet or golang text-templates to make settings user extendable
3. Allow managed settings to specify _migrations_ that are understood.

Alternative Solutions

Currently using a mix of home-manager and other tooling (including custom migration scripts) to generate defaults but have no method to get "extend" a setting, like statusline.

Priority

High - Significant impact on productivity

Feature Category

Configuration and settings

Use Case Example

Example scenarios:

Settings migrations:

1. we create a plugin marketplace within a company
2. we need to change the URI, and some plugin names, or migrate per-team plugin marketplaces to the main one
3. currently, only custom migration scripts work for this

Extendable settings, optional defaults:

Statuslines, some environment variables.

Additional Context

_No response_