existing comments

[lightninglu10]

No description provided.

[github-actions]

Review Summary

This PR threads existing human review comments into the autonomous agent's context.

Key changes

• Adds an section to the system prompt so the agent understands how to handle prior comments and emoji reactions.
• Introduces an ExistingReviewComment type and formatting helper to include prior review comments in the initial agent message.
• Updates the GitHub Action to fetch non-bot review comments into pr-comments.json.
• Updates ReviewService to load pr-comments.json and pass existing comments into reviewFullDiff.
• Extends tests to cover the new reviewFullDiff signature and default empty existingComments when there is no pr-comments.json.

Review notes

• The new ExistingReviewComment type is consistently used in src/index.ts, src/review-service.ts, src/agent/index.ts, and tests.
• Filtering out bot comments in src/index.ts looks correct and should avoid the agent reacting to its own output.
• The formatted block appears well-structured and matches the new policy in the system prompt.
• Tests for ReviewService correctly assert the additional existingComments argument.

No blocking issues found; implementation is cohesive and consistent with existing patterns.