Render external QML text as plain text

[debpalash]

Summary

• force CLI/catalog-derived status, error, catalog, and device values through Text.PlainText renderers
• cover the reviewer-cited shared status-card title and detail sinks
• add a CI regression check for every hardened external-data sink

Security

This prevents Qt automatic text-format detection from treating external values as rich-text markup.

Validation

• manifest validation
• QML formatting for Panel.qml and Service.qml
• shell syntax validation
• plain-text sink regression check
• detached download-state test

Addresses the blocker in omacom/omarchy-plugin-marketplace#2942.