Advanced/Custom Mode: Raw JSON authoring and fluent fallback #346
Description
Add support for a "Custom Mode" where users may open/edit automations as raw ConfigJson/RuleConditionsJson (JSON editor), as described in AutomationAuthoringArchitecture.md.
- UI toggle enables Custom Mode (JSON editor for config and rules)
- Saving in Custom Mode disables further editing in fluent UI (form becomes read-only and displays best-effort sentence rendering; unknown rules/fields marked as "custom")
- Users may view JSON at any time; rehydration to fluent UI if config/rules are parseable
Exit criteria:
- Custom Mode toggle present and functional
- JSON edits properly update ConfigJson/RuleConditionsJson
- Fluent UI disables and best-effort renders when config/rules unparseable
- Test all state transitions and round-trip safety