Turn review comments into work

Comment on a line, then hand the comment back to the agent as context. content may be empty when diffCommentsContext is present, which is how a comment-only turn works.

bash

curl -s -X POST \
  "https://app.kosuke.ai/api/projects/$PROJECT_ID/chat-sessions/$SESSION_ID/preview/diff/comments" \
  -H "Authorization: Bearer $KOSUKE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "filePath": "src/search/route.ts",
    "side": "new",
    "startLineNumber": 42,
    "endLineNumber": 44,
    "body": "This leaks the limiter across tenants.",
    "lineSnapshot": "const limiter = new RateLimiter()"
  }'