Address the review of this pull request:
- A failed image upload keeps the Host's attachment refusal reason. The
thumbnail of a refused image names the reason instead of offering a
retry that cannot succeed, and Enter while uploads hold the send names
the first failure; a transport failure still offers retry, and an
image without a file name uses the pending-image label.
- An image upload stops reading at the smaller of the per-image and
per-message byte limits.
- A carried image draft moving to a Session that sends images inline
drops its upload instead of staging it again.
- The image upload ready state no longer carries an unread image ref.
- Docs describe stored-image admission and the command image path, and
the attachment rail test builds typed props instead of casting through
unknown.
Yichen Jiang
b22cf68e50