Fixes from the review of api.files:
- `files.attach` to a new draft runs `onBeforeAttachmentUpload` for each
file and the server's total size limit before `compose.open`, which
runs neither; refused files come back in `refused`
- a write is refused when a folder above the target is missing from the
listing, instead of counting it as not shared
- `onFileMove` reports the item as it was, from where it was, like the
Files app's own move
- writes are counted against the 20-a-minute limit before the drive is
listed, so refused writes count and cost no listing
- reads stop the download past 20 MB (`fetchBlobArrayBuffer` with a
limit) and answer `too_big` when the listed size was wrong
- when the server refuses the new content of a replaced file, the old
version's copy is taken out of the trash again
The two getText assertions on `fetchBlobArrayBuffer` now expect the
account (undefined for the own drive) and the byte limit, since the
call passes both.
The assistant's new host calls come in four areas (context, actions,
Files, the panel in every view), built side by side. Each area gets its
own files under lib/plugin-sandbox/assistant for its permissions, method
table, dispatcher, host feature flags and sandbox methods; the shared
files only read the merged result. No area adds anything yet. The host
features test now compares against the core flags plus the areas' flags.
Linus Rath