Add a --dry-run flag that shows what would happen without actually committing, rejecting, or modifying task status.
Requirements:
- Must work with task ID: pi-review --dry-run t-123
- Should run all verify commands (lint, bild, test)
- Should show the diff and review prompt
- Should show what verdict pi would give
- But should NOT: commit, revert, add comments, or change task status
- Print a clear message that this is a dry run