Currently Listening: finished is 90% played, not read

Opening an episode marks it read, so filtering on read hid every
episode anyone had started. The player now also reports the length it
measured, filling in one the feed left out. Fixes #14.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/history.md

@@ -6,6 +6,21 @@ reasoning lives. New write-ups go at the top.
 
 See [README.md](../README.md) for what the thing is.
 
+## 2026-09-15 — Currently Listening, empty for anyone who opens what they play
+
+Issue #14: an episode 32 minutes into 41 was missing from Currently Listening, which said nothing
+was in progress. The filter was "position past five seconds and unread", on the reasoning that
+`markPlayed` marks an episode read at 90%. But opening an item marks it read too, and you open an
+episode to play it. In production every one of the twelve episodes with a saved position was read,
+so the list was empty for everyone. The browser test for it had set the episode unread before
+checking, to cope with an earlier test having opened it, and so tested around exactly this.
+
+Finished now means the saved position is 90% of the episode's length or more, the same line
+`markPlayed` draws, and read plays no part. Three of those twelve episodes had no length in their
+feed, and with no length there is no telling finished from started, so they would have stayed
+listed for good. The player now sends the length it measured with each saved position, and that
+fills in a missing one, never replacing a length the feed gave.
+
 ## 2026-09-15 — davewiner's 922 rows, retired at last
 
 davewiner's OPML subscription left config.toml before `retire_group` existed, so nothing ever