Add "Show Reference Mode" to Text0

[Railly]

Description

Implement a new "Show Reference Mode" action in Text0.

When triggered:

• Display the current document in read-only mode.
• Highlight parts of the document that were extracted from references/memory using LLM analysis.
• Original content (written by the user) will be differentiated visually.
• On hover, a tooltip will show:
  • Source reference (if detected)
  • Other metadata (e.g., confidence score, link to source if available)
• Calculate and display a "Percentage of Originality" metric for the document (similar to plagiarism detectors, but contextual to memory/reference sources).

Notes

• UX for triggering the mode is TBD (could be a button, shortcut, or menu action).
• Focus first on backend pipeline:
  • Extract reference matches.
  • Classify text spans.
  • Compute originality %.
• Frontend:
  • Render spans with different highlights.
  • Tooltip behavior on hover.
  • Read-only protection.

Goal

Give users insight into what parts of their document are referenced vs original, enabling better editorial judgment and ethical publishing.

[linear]

CAI-23 Add "Show Reference Mode" to Text0