Feature: Enhanced GitHub PR review submission workflow

[hay-kot]

Description

Current PR review submission is basic - need a complete workflow with preview and submission options.

Proposed Features

1. Review Preview Before Submission

Before submitting, show a summary window with:

• All comments to be submitted (grouped by file)
• Total comment count
• Review type (comment, approve, request changes)
• Option to edit/remove comments before submission

2. Complete Review Workflow

Support GitHub's full review API:

• Comment: Submit comments without approval status
• Approve: Approve the PR with comments
• Request Changes: Request changes with blocking comments
• Pending: Save as pending review draft (not submitted yet)

3. Review Submission UI

Add commands:

• :DiffReviewSubmit - Open submission dialog
• :DiffReviewSubmitApprove - Quick approve with comments
• :DiffReviewSubmitRequestChanges - Quick request changes

4. Submission Dialog

Interactive prompt showing:

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
  GitHub PR Review Submission
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Review Type: [Comment] [Approve] [Request Changes]

Comments to Submit (12):
  src/main.lua (5 comments)
  src/utils.lua (3 comments)
  src/config.lua (4 comments)

Overall Review Comment (optional):
[________________________]

[Preview] [Submit] [Cancel]

5. Post-Submission Actions

After submission:

• Show success notification with review URL
• Option to clear local comments
• Option to keep comments for follow-up

Benefits

• Prevents accidental submissions
• Reduces API errors from malformed reviews
• Matches GitHub's web UI workflow
• Better control over review type and comments