Refresh buttons turn from the press to the end of their scan; quick checks keep the count (#232, #233)

The buttons followed the feeds being checked, so they stopped between one feed and the next;
7ecbe82 held them for 600 ms over each gap. Now pressing one starts it, and scan_done stops
it only when it is the end of the scan asked for: scan_done carries `only` and `forced`, so a
scheduled scan finishing first does not stop a button whose scan is queued behind it. An
error event, a job that failed without a scan_done, stops them all.

A row's spinner stood in for its unread count from the moment its feed was checked; most
checks take milliseconds, so each count blinked as the scan went by. It now waits 300 ms.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/ipx/CHANGELOG.md

@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Check every feed looks up the site icons of feeds without artwork a few at a time, alongside the fetches, instead of one after another (#228).
 - A feed's server that sends nothing for 15 s is given up on, instead of holding a scan for the full 30 s; a feed that keeps sending still has 30 s (#230).
 - A scan's trace names the feed each fetch is for (#229).
+- `scan_done` on the event stream says which feed or folder the scan was limited to and whether someone asked for it (`only`, `forced`), so a page can tell the end of its own scan from a scheduled one's (#233).
 
 ## [1.1.0] - 2026-10-13