Bug: Inline images lost on IMAP accounts in Thunderbird 143 with Advanced Composer

Hello,

After updating to Thunderbird 143 (Windows and Linux, 64-bit), Advanced Composer stopped preserving inline images when replying/forwarding messages from IMAP accounts.

• On Thunderbird ESR 140.x → works fine, inline images preserved with cid: references.
• On Thunderbird 143 → Advanced Composer inserts imap://…/fetch… links instead of cid:, so inline images are not displayed in the compose window.
• Issue reproduced on both Windows 11 and Linux (Flatpak).
• Account type: IMAP (Outlook 365).

Steps to reproduce:

1. Receive an HTML email with inline images on an IMAP account.
2. Click Reply (with Advanced Composer enabled, template using %quotedText%).
3. Inline images disappear — src="imap://..." is inserted.
4. Disabling Advanced Composer → Thunderbird shows images correctly.

Expected result:
Advanced Composer should preserve original HTML, including inline images with cid: links.

Actual result:
Inline images replaced with imap://fetch references, message body shows placeholders instead of images.

Environment:

• Thunderbird 143.0.1 (Windows 11 64-bit, Linux Flatpak)
• Advanced Composer latest version from GitLab
• Account: IMAP (tested on Outlook 365)
• Works correctly on Thunderbird ESR 140.3.1