Update log
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Version 1.2.2
- Each copy in a duplicate group is now independently KEEP or DELETE;
tap a row to flip just that row, rather than accepting the extension's
auto-selection. A safety guard prevents marking the last remaining
KEEP as DELETE. Preview moved to a small eye icon so the row body is
a clean toggle target.
- New Skip Trash option, default on. Stops treating a message you kept
in one folder and its already-trashed copy as a duplicate.

Version 1.2.1
- Skip Archives now defaults on. Gmail exposes labels as IMAP folders
and its "All Mail" folder contains every message, so scanning
archives makes every Gmail message appear as a duplicate and
deleting from those folders has non-obvious server-side effects.
Turning Skip Archives off shows an inline warning explaining the
risk before proceeding.
- Folder tree hides any folder type currently being skipped, and the
"N of M selected" counter reflects only scannable folders.

Version 1.2.0
- Scans run in a detached window that stays open even if you click
elsewhere in Thunderbird. Setup still happens in the toolbar popup.
- Cancel button next to the progress bar interrupts a running scan
between folders.
- Account filter above the folder tree limits the visible list to one
account at a time. Select all / Select none respect the current
filter so bulk-toggle only touches visible folders.
- Cascade selection toggle in the folder tree header controls whether
checking a folder also checks its subfolders.

Adds diagnostics with automatic write of log to user's configured download location (Preferences → General → Files & Attachments → "Save files to")