Let the reader pause a download, and draw its progress as a ring

[rbioteau]

What this is

The pill has never had a control a reader could use deliberately: the only way to stop a download was to tap a percentage, which silently cancelled and threw the pages away. Now that the queue resumes from the pages it kept, a copy on its way offers Pause, a copy that stopped offers Resume / Retry, and a copy that is here is a mark that cannot delete anything — removal is the row's trailing swipe, which now arms for a copy that stopped on its way as well as one that is here.

state	ring	glyph	word	row's own line
nobody asked	—	save	Save	—
queued	its pages	pause	Waiting	—
downloading, no page count yet	turns	pause	Preparing	—
downloading	fills	pause	Downloading	—
paused / pausedByUser	frozen	play	Resume	Paused
failed / interrupted	frozen	refresh	Retry	which stop it was
saved	—	check	—	—

The three decisions worth a reviewer's eye

1. A pause the reader makes is a state of its own (pausedByUser). The app's paused is resumed without being asked whenever the app comes back to the foreground or a profile is entered, so a reader's pause written as the same value would be undone by the next app switch. Nothing but a tap resumes theirs; the launch strip does not count it; "not now" leaves it alone.
2. A copy's progress is a ring; a bar on a cover is reading progress. CoverProgressBar pins the reading bar to a cover's bottom edge, so the download's own progress is a ring wherever it is drawn — inside the pill, around the glyph — and the two can never be read for one another on a row that carries both.
3. A copy that is on the device belongs to the shelf, whatever its record is doing. A refresh runs with the copy it is replacing intact, so its record is both saved and in flight; that chapter was drawn twice, once in the shelf and once among the copies on their way, and a copy the reader can already read was announced as something that stopped. The tab's sections and the launch strip now list the same set.

Where it sits

Inside #97's area, and not the same thing as #102: that ticket removes the pill for a press-and-hold gesture and is blocked by #98. This keeps the pill and gives it the controls the queue now supports. #102's two rules that can be honoured today are honoured — the saved mark is not tappable, and a saved copy is removed from the trailing pane, which still confirms.

Verification

flutter analyze clean; 919 tests pass (flutter test), nine of them new. Two are the argument and each fails without its fix: a reader's pause survives the app going away, and a launch does not ask about a refresh that stopped. One more pins that the tab's rows fit a 390pt phone — it loads the real face, because the test environment's own font is twice as wide as Space Grotesk and would otherwise fail a width no phone has.

Not verified: the pixels. There is no image test in this repo, and the pill's ring around its glyph wants an eye on flutter run -d linux.

Known consequences, deliberately left

• The same bin deletes a partial in one tap and asks before deleting a saved copy.
• _RefreshCopy still wears a fill, where the pill no longer does: it appears only on a copy the server has stopped agreeing with, where a bare word would not be noticed.
• savedChapterIdsProvider hands out a fresh List on every state change, so the shelf rebuilds more than it needs to — pre-existing, untouched here.