Add validation mode to review diffs against requirements/plans

[williycole]

Description:

Feature request: Add a plannotator-validate mode that verifies code diffs against linked requirements / plans to aid in review.

Use case:

When reviewing a PR, it's useful to check:

• Which requirements does this diff address?
• Are there gaps (requirements not covered)?
• Is there scope creep (changes outside the plan)?

Reference:

Proposed approach:

• New plannotator-validate skill/command
• Takes plan do as input for requirement context
• Shows which hunk addresses which requirement
• Flags gaps and unexpected changes
• Can be invoked alongside regular plannotator-review

[williycole]

I have a project I made to do this that I've been using before discovering plannotator, and I'd really like to use that functionality here. If anyone is curious I can share it here. I wouldn't mind tackling this if allowed. Please yeet this issue if this ask isn't wanted. Just wanted to drop my idea here.

[williycole]

Reopened because I thought the skill:plannotator-visual-explain skill did this, but it doesn't quiet do what I had in mind.