* perf(json-editor): improve JSON editing experience
- integrate Yace for syntax highlighting, history, indentation, auto-closing, and smart line breaks.
- add copy support, cursor location feedback, and synchronized content and line-number scrolling.
- extract JSON editor utilities and cover key interactions with unit tests.
* perf(system-settings): improve JSON configuration editing
- replace raw JSON textareas with the shared editor for highlighting, validation, copy, and formatting.
- preserve field-specific examples and make placeholders visible through the transparent editor layer.
- remove duplicate formatting controls while keeping existing form validation and save behavior.
* perf(json-editor): standardize JSON inputs across admin settings
- replace pure JSON textareas with the shared editor across system settings and channel workflows.
- preserve form focus, validation, placeholders, and visual or JSON editing modes.
- add happy-dom component coverage for form bindings, controlled updates, and formatting.
* fix(json-code-editor): address accessibility review findings
- Drop the unconditional aria-label that overrode every field's
label-derived accessible name; add an optional ariaLabel prop and
set it at call sites without an associated label
- Associate standalone Labels via htmlFor/id in channel-affinity views
- Hide the highlight mirror and line-number layers from the
accessibility tree (aria-hidden)
- Give the line-number gutter an opaque background so horizontally
scrolled code no longer slides under it
- Degrade to no scroll sync instead of destroying the editor when the
line-number layer is not found
