Reply to all recipients of a Gmail message with automatic thread handling.

• Replies to the original sender and all To/CC recipients; use --remove to exclude specific addresses
• Supports plain text and HTML body content, file attachments (multiple), and optional CC/BCC fields
• Includes --dry-run mode to preview the request before sending, and --from for send-as/alias accounts
• Requires Gmail message ID and reply body as mandatory inputs; fails if no valid recipients remain after exclusions