spike(ai/editor): prototype local AI-assisted PDF edits with preview and undo #79

Explore AI-assisted editing without promising unrestricted Word-style PDF rewriting.

The prototype should translate a local-language request into bounded editor operations already supported by OffPDF: overlays, annotations, links, forms, redaction, and page operations.

Guardrails

• Depends on the direct-editing foundations and the local runtime.
• The source file is never modified in place.
• Every proposed change is visible before export and individually removable.
• Unsupported edits are reported clearly; the model must not simulate success.
• Secure redaction uses the verified redaction path, never a visual cover-up.
• The full proposed operation list can be inspected and undone.

Deliverable

A technical prototype on representative fixtures, plus a short report on quality, latency, failure cases, and which operations are safe enough to productize.