[v0.8] Optional AI-assisted reviewer action extraction

[JUhalt]

Goal

Optionally accelerate Reviewer Response Matrix setup without making AI a requirement or silently sending scholarly content off-device.

Scope

• Explicit user-triggered extraction of reviewer/editor comments into candidate action items.
• Prefer local model support where practical.
• Permit optional external AI providers only with explicit configuration and per-use user awareness.
• Preview-before-apply workflow.
• Preserve source text and provenance for accepted extracted items.
• AI remains an enhancement to the Reviewer Response Matrix, not a dependency.

Acceptance

• Feature is disabled/unconfigured by default.
• PaperRoute remains fully functional without any AI provider.
• No manuscript or reviewer content is silently transmitted externally.
• Extracted items are candidates until the user explicitly accepts them.
• Provider/extraction failure never changes the underlying decision or manuscript data.