feat(cli): add create-with-session-id support
rename public task id flag to --create-with-session-id
validate session ids as UUIDs for create/resume and stdin start.taskId
add integration coverage for create+resume loading correct session
feat(cli): support images in stdin stream start and message commands
Add optional `images` field (array of base64 data URIs) to the `start` and
`message` CLI stdin stream commands, allowing callers to attach images to
prompts. The images are validated, forwarded through the extension host, and
included in queued messages.
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
