Adjust code review feedback message

[tobeycodes]

When no changes are requested we send a response saying LGTM and ask to address feedback but there is no feedback to address.

In my opinion I would suggest that we do not send Please address this feedback. if LGTM - no changes requested. is the feedback.

My agent got confused and asked me to clarify whether there was feedback or not on a couple of occassions.

# Code Review Feedback
LGTM - no changes requested.
Please address this feedback.

plannotator/packages/review-editor/App.tsx

Line 533 in d2238ac

feedback: 'LGTM - no changes requested.',

plannotator/apps/opencode-plugin/index.ts

Line 233 in d2238ac

text: `# Code Review Feedback\n\n${result.feedback}\n\nPlease address this feedback.`,

plannotator/apps/pi-extension/index.ts

Line 258 in d2238ac

pi.sendUserMessage(`# Code Review Feedback\n\n${result.feedback}\n\nPlease address this feedback.`);

[backnotprop]

In-progress